London Day Trip Walking

Saturday I did a new thing, a day trip to London.
I know it's not the first time I visit a European capital in one day thanks to a low-cost flight, but it's the first time I do it without spending a euro, or rather without spending a pound :)

London in one day, walking without using public transport

As usual, the necessary premise: one day just is not enough to see a big city like London, but we say that with a good step and with a good organization, you can see the main things, especially if you decide to move even with public transport.

In my case however, I had already been in London, so I decided to devote myself to what I had not been able to see the first time - the British Museum.

The primary purpose of this day trip to London was therefore to see the British Museum, then all that would come out would be well accepted.
But let's go for the order, the flight.

Looking for the internet, not even a week before, I found an unbeatable offer to fly to London in the day, with a good time at 8am and a return flight at 6pm.
Of course, it was not the nearest airport where I would land, it was Stansted airport, but in the end, with a good train, in about 40 minutes you're in town.
So I got the Stansed Express, the equivalent of our Malpensa Express, but it's definitely much cheaper (about 30 euros if you do not book it much sooner).

But we come to the London speech on foot in one day.
Because you will walk to you, there was already little time left.
True, but having spent a fair amount of euros for moving from airports to the city (so much so that it has reached the cost of the plane), I said, "If I change the money it ends I'll drop another 50 euros in fluency" .
From there my decision to book all the trips from Italy, to bring me food, and to travel on foot, without spending a penny then :)
I could also take the daily card of the car from Italy, but it would never arrive in time, so here I am here to walk London on foot.

According to the logbook, I would arrive by train at Liverpool Street Station, which, looking at google maps, did not seem so far away from my destination.
So I decided to get to the British Museum on foot, so much during the hour (45 minutes actually) walking, I would have seen and mostly photographed so many things, making an itinerary that I probably skipped last time.
After arriving at the museum, having first studied the 10 things not to miss the British Museum, I started the visit, bouncing from room to room.

I do not know if I've seen it all, maybe some room has escaped (I've been a couple of oats, I'm not one who reads all the insignia: p), but I was very pleased with my visit.

A small note about the British Museum: it's one of the largest history museums in the world and it's free ... a beautiful moral slap for some of our museums, which in comparison are microscopic and discreetly dear ones (eg 900's Museum) .

Anyway, after the museum, a little break in a park for lunch at the bag, and I'm ready to take a nice walk around the city.
Initially, I had thought of going to see the famous Binario 9 3/4 (Platform 9 3/4), where Harry Potter and his mage friends teletrasportano, then I remembered not to be a fan of the saga: p
More than that because I had to go to the opposite side of all the other attractions.
Then, walking along the streets of London, I noticed that the Potter is almost a national hero from these parts, so I'm a little sorry.

Another attraction that I skipped is Little Venice, a London area comparable to our Venice, and a bit even in Amsterdam.
However, having seen them both, and always for the talk that was on the opposite side of where I wanted to go, I jumped it reluctantly.
But then I did it again, with a walk lasting until about 16, where I saw many things in London, some already seen before, other unpublished (eg the Chinatown ceremony for the Buddha's birthday anniversary, and a ' Isolated musical parade with a lot of military).

Of course, I'm also a bit off the Thames, admiring the Big Ben, the Westminster Abbey, the London Eye, St Paul Cathedral, the Shard, some parks, the London beach, and getting to admire the Tower Bridge.

In the end, exhausted after a day in London on foot, I went back to take the shuttle-train to the airport, and returned to Italy.

What about this yet another low-cost experience?
First of all it was a nice exception, for two reasons.
The first was to find the flight at a very low price without much notice (usually I move a few months earlier), the second was the choice not to change money, and to make a day trip at no cost (if you exclude Travel to and from the city).

In all this walking, I obviously also shot some nice videos, which I added to last year's playlist, viewable at this address:https://www.youtube.com/playlist?list=PLCBrso9WwkFYlTz1ejdFtG65ORx2C3KiA



London is a beautiful city, certainly to be deepened in its details, but if you are not a fanatic of museums, and you like to move independently, without staying locked in a place, then such a tour has its own why.
In my opinion, there are also many trips to London (if they cost just as much in this case).
It's true, for a taste of the major attractions just one day (if you exclude those a little out of the way), especially if you travel with the metro, but London has so many things to look into, so if you like the taste, Then you will definitely want to go back, just like you did to me.

>> London 2017 photos <<

Going to live in the Philippines: Pros and Cons

The network is full of articles that encourage Italians to go abroad.
If you are a frequent social networking user, you will definitely be stuck at least once in articles titled "Here are the countries where you can live with 300 euros a month."

Being also one of the many who dreams of fleeing from Italy, for some time I have started to study some of the most popular places for those looking for dream beaches and a good climate.
In this article I will speak to you about the Philippines.

Why go to live in the Philippines?

The Philippines is a Southeast Asian state located in the Pacific Ocean.
The Philippine Archipelago consists of 7,107 islands distributed in three main regions: Luzon to the North, Visayas in the center and Mindanao to the South.

What attracts thousands of tourists each year in the Philippines is the beauty of their beaches.
The Philippines, in fact, offers those who take the trouble of having more than 10 hours of air travel to visit them, beaches that have nothing to envy to those of the Caribbean, with the difference that the Philippines are a low-cost location.
For the lovers of the sea, unspoiled nature, snorkeling and diving, the Philippines are a must-see destination.
If you want to get an idea of their beauty, read this post on my trip to the Philippines.

Given the beauty of the Philippines, it's easy to understand why a person, enthusiastic about their vacation, can think of giving up everything and moving there.

If I have to be honest, even at first I had a thought, even before I went to visit them as a tourist.
I had discovered the Philippines looking for google places where it costs less to live, ending up on those infamous articles where only the beautiful things of a place tell you.
Enchanted by beautiful photos and promises of savings, I started to document me, I planned the trip, I went, I came back, I searched for land sales ads on the internet, and when I found out that with the money selling my current Home I could buy a whole resort in the Philippines, I started fantasizing ...

But then I've documented it better, I've done a lot of online searches, I've been enrolled in groups from Italians living in the Philippines ... and I understand that it's not all gold that glitters!

Do you really live with 300 euros a month in the Philippines?

The answer is no!
Anyone who claims the opposite is forgetting to specify some details not just recently.
Yes, if you want, you could live in a remote, non-touristy little village, in a hut, cultivating a land and buying only local products, and so you could really live with little ... but honestly, who would do it?
Filipinos live with little because they have little! Not everyone obviously.
The average monthly salary of a Filipino is only a few hundred euros, if it's fine.
It is no coincidence that Filipinos who come to work in Italy, with the money they send home, have a whole family.
I'm talking about people living in villages with few services. Do you really want to live that way? Yes? Even wanting you can not! Or rather, you can but it is complicated to implement (later I explain better why).
Great cities like Manila, where there is every kind of comfort and there are skyscrapers that we in Italy dream about, are perhaps even more concerned with Milan.

Pulling the sums, no one gives you anything, if you want to live with little, you have little.
If you want the services, pay them and cost almost like in Italy (if not more in certain areas), if you do not want them, it is a great risk considering the area you are in (read the pros and cons that I have Written below to better understand).
If one has to live almost in misery, then perhaps it is better to stay in Italy, going to live in some villages where life costs a little less.

 

How to move to the Philippines

To move to the Philippines is not enough to take the plane and leave.
I will briefly explain the chances you have to go to live in the Philippines.

Attention, all the information below is indicative and subject to change (if not inaccurate at startup: p), before making any decision on the internet for official sources.

First, if you do not have a fixed job / activity / rent and want to stay a little longer to study a little better the country, you will need a longer visa than the tourist one, which can be kind of 6 months if I do not remember (And of course you pay).
This visa can be renewed from time to time, with the obligation to leave the country every 3 years.

If you are retired instead, you can stay in the Philippines with a resident's visa, leaving a certain amount in a Filipino bank as a deposit, and making them pay your pension every month.
If you do not have a pension, the amount to be paid will be a bit higher.
After 10 years of permanent residence, you may also be able to apply for Filipino citizenship.

So on a level seen, if you have some money aside, being able to stay on the Filipino ground is a feasible thing and not too complicated.

Well, now that you understand how to stay in the Philippines, you just have to buy a home ... Alt! The real difficulties are coming now!

Buy a home in the Philippines

To buy home and land in the Philippines is not enough to have the money!
The Filipinos, probably to protect their country, have created special laws to prevent rich foreigners from acquiring all their lands (my personal hypothesis about the existence of these hateful laws).

First of all, the ground: if you want to buy land in the Philippines ... you can not!
Or rather, you can not if you are not Filipino.
But if you have a Filipino wife who you trust, you can put everything to her and you're affiliated ... but if you're litigating? Beware ... following the online groups I've read all about stories about scams and strangers scared by women or their families (although this actually seems to me much more in Thailand).

Another opportunity to buy land or open a business in the Philippines is to create a Filipino majority corporation with a minimum of 3 Philippine partners and a share capital of at least 4000 Euros (add approximately 1,000 Euro for its opening).
In this society you will be the president, with full decision-making powers, and you can then name the ground and everything else on behalf of the corporation, and thus actually circumvent the limit of not having land in the Philippines.
Okay ... but willing to find Filipino partners to trust ... it goes without saying that if you do not trust trusted risk of ending a victim of some scam.

There is then the possibility of renting the land for about 25 years (paying a decent nest).
In my opinion however, this solution is fine as long as you are young and shiny.
However, when you begin to lose strikes and maybe you are alone, at the end of the contract it may not be so easy to deal with the bureaucratic part ... maybe in the meantime the laws have also changed, or perhaps for some reason they no longer want to give that Land ... always remember that you are in a foreign land and your rights may not be guaranteed as it would happen in your country of origin.
Not to mention that if a child may want to leave everything inherited to them, so if they are Filipino one day they may be able to buy the land you have now rented, if they are Italian they will have to do them all the trafila ...
I will be old, or maybe I will only be possessive, but for my future I would like to live in a place all my own, not renting :)

Another solution is to go to rent or buy a house in a condo where there is a majority of Philippine condos / owners.
This is very simple in the cities, a little less if you want to live in a chalet.
You should look for some residential complex and then say goodbye to the idea of ​​the lost and cheap cottage in the middle of nothing :)
However, by pulling out the sums, the more residential condo solution with deposit, would be the easiest option to implement, and perhaps even the one at less risk of scam.

There is another problem in the Philippines, of which the famous articles "all about it" do not talk to you ... corruption!
As I read, Italy in comparison with the Philippines is a country full of honest people :)
I've read about scams, scams, blackmails, where for example they get you started, but then you block them and they do not give you permission if you do not give up so many good soldiers.

But the scams that can be made through corruption are of another kind and can hit you in the daily life.
For example, a scam I've been told is that of some girls who are before us, and then they denounce you by finding some bruises on them (maybe made by their true boyfriends).
And there are serious problems, especially if I do not really care who gives you a loophole underneath ... so I can even tow in some countries!

With this obviously I do not want to discourage you, there are several Italians who have managed to live in the Philippines and are now more or less happy.
Even if it is true I understand that most of them have already started with a Filipino wife from Italy ... if you are alone and you do not know anyone is much harder and you have to be careful not to bother!

Working in the Philippines

I also add this paragraph to make you notice another thing:
In the Philippines, foreigners can not do all kinds of work.
There are in fact some foreigners' jobs, such as, if I remember (google for security), sell things.
I guess, however, if one looks for a job as an entrepreneur, a way to open his shop can also find it, but it always falls into the issues mentioned above.
If you are looking for an employee job and you can find what you can do even if you are a foreigner ... well, the Filipino paychecks are really miserable!
Different is the story if you live in the Philippines working for a foreign multinational that pays you well ... then you start thinking;)

Pros and cons of going to live in the Philippines

While some pros and cons are subjective, below I will list a list of reasons that may encourage or discourage anyone who thinks about leaving everything to live in the Philippines.

Pros

• Beaches, sea and uncontaminated nature
  If you are looking for unspoiled nature and postcard beaches, in the Philippines your expectations will not be disappointed.
  Several areas of the Philippines are also famous for snorkeling and scuba diving
• Cost of living
  Overall certainly lower than in Italy, as long as you do not decide to live in metropolis or in very touristy places
• Language
  A good news, most Filipinos speak English!
• Religion
  About 90% of Filipinos are Catholics.
  This obviously does not guarantee a behavior to give the other cheek, but we say it is a cultural meeting point with our officially secular country
• Health care
  I put it as a pro if you live in town and if you have insurance, because it seems to be very high
• Climate
  Tropical climate where you do not really have the cold and you can bathe in the ocean at any time of the year.

Cons

• Difficulties in buying house and land
  Read the paragraph above
• Delinquency and Weapons
  In large urban centers there is a bit of delinquency and you have to be careful where you go.
  However, I have read that some small villages have been afflicted with this problem, where police might be a problem because of corruption ...
  Let us also point out that in the Philippines anyone can buy a weapon, and the situation may start to look a bit worrisome
• Different culture
  There are some profound differences with our culture, as well as their way of doing and behaving.
  According to those who live there, with the Filipinos it takes a lot of patience!
• Culture absent
  This may seem an offense for Filipinos, but if we compare Filipino to Italian culture ...
  However, if you do not mind visiting museums, exhibitions and ancient architectural jewels (though in their small there are also them) ... in short this is a counter degustibus
• Health care
  I also put it in between for two reasons: the first is that you have to do health insurance if you do not care (if you do not have the money to pay), the second is that if you imagine living in the Philippines to stay Away from the city, in a quiet seaside ... maybe in those cases will have at least one outpatient clinic nearby, but in case of serious problems, now that the helicopter arrives and takes you to the hospital City ... bye bye
• Poverty
  Never underestimate the fact that it could be a problem to move to a relatively poor place.
  First of all, unlike going to live in places like the Canaries, where you can easily camouflage among the many non-natives and no one will ever say anything, in a place like the Philippines you could always be seen as the rich alien (and maybe To be pushed).
  In my opinion, the more a place is poor and the less life can be ... of the kind that can kill you for nothing ... but even without thinking of it as a pessimist, if you are considered rich, it will nevertheless be higher the possibility that someone may Knock on your door in search of something (money), who are the relatives of your Filipino wife or neighbors in your remote village
• Corruption
  As explained above, corruption in the Philippines is a big problem!
• Climate
  The climate is a strong point but also a weak point in the Philippines.
  Being subject to the rainy season, there may be times of the year with uninterrupted rain, and yes one suffers ... but the really serious thing is that every year the typhoons arrive in the Philippines.
  Mostly typhoons affect only certain areas, so if one studies well before moving, it slightly reduces the risk, but this is not always the case, and there have been cases like for Haiyan, where most of the Philippines have suffered serious damage There have been many victims.
  It is true that most of the victims are poor people who can not afford robust homes, but considering the fact that with the rise of global temperature the climate is getting worse and there are also those who say that in future events such as typhoon Haiyan Can happen more often ... in short, the climate factor is not to be overlooked!
• Religious and rebellious minorities
  Like other countries in Southeast Asia, the Philippines have some problems with some armed rebels in some parts of the country.
  In addition, there is an Islamic minority in the south, which attacks from time to time.
  If you are careful where you go, there is no risk in theory, but let's say that having two issues in my country is not reassuring to me.
  Let us also add that in some areas, even tourist-like Palawan, in the past have raped foreigners to ask for a ransom, and that this thing has happened recently in another area to an Italian restaurateur ...
• Diseases
  Even though it is part of the health system talk, it should be noted that in some areas of the Philippines there are still malaria and dengue diseases ... so be careful where you go.
• Unspoilt nature
  Nice to see, but not for everyone.
  If you are afraid of spiders and snakes, maybe the Philippines will not do it for you
• Distance from your country
  If you are tired of your country, so much distance will seem just a good thing to you.
  But if for some reason you have to return often, or even just occasionally, to your homeland (to go to your relatives or for other reasons), it's a great journey ... both as time and as cost!
  Maybe when you decide to take the big step do not think about it or you do not have a chance to come back often ... but if you are forced to change the plans, it may be a great problem for your pockets.

It's all, I hope I did not have you too discouraged :)
As I said before, this is just my subjective assessment, matured after collecting some information on the internet and having seen some things in person.

For me the Philippines are still a beautiful country, which one day I would definitely visit again ... but as a tourist :)

Maybe whoever made the big step and did it was more motivated than me ... or simply more courageous :)

Genetics (8/8): DNA and genomic technology

Most of the methods used to clone DNA fragments have some common features, for example there is a method that uses bacteria and their plasmids.
Plasmids are small molecules of circular DNA that replicate within bacterial cells, regardless of the bacterial chromosome.
In order to clone genes or fragments of DNA isolate the bacterial plasmids, insert an extraneous gene inside the plasmid and finally reenter it into the bacterial cell where it is reproduced by forming a cell clone that also contains the foreign gene and this bacterial clone It will produce the protein encoded by the foreign gene.
Cloning can be used to obtain protein products for research or mass production of specific genes.

Restriction enzymes are enzymes that cut DNA molecules on a limited number of specific regions.
Restriction enzymes protect bacteria from foreign DNA and work by cutting this DNA through a process known as restriction.
Most of these enzymes are highly specific, and the bacterial cell protects its DNA from restriction by the addition of methyl groups (-CH3) within sequences recognized by restriction enzymes.
The recognition sequence is referred to as a restriction site, these sites are usually symmetrical and have the same sequence 5 '-> 3' consisting of 4 or 8 nucleotides, recognizable on both filaments but oriented in opposite directions.
Restriction enzymes cut the bonds on both filaments, and since these sequences are usually present in the DNA multiple times, the same enzyme can perform more cuts.
When subjected to the action of a given enzyme, copies of a DNA molecule always generate the same set of restriction fragments, so a restriction enzyme cuts a DNA molecule in a reproducible way.
In the product fragments there is at least a short single strand end region, said adhesive end, which will temporarily collide with few hydrogen bonds on the single strand of the other DNA molecules cut with the same enzyme, and these couplings can be stabilized with the enzyme DNA ligase, which holds the filaments together, catalyzing the formation of phosphodiester bonds.
It has recombinant DNA, that is, a molecule obtained from the union of DNA from two different sources.

The original plasmid is called a cloning vector and is a DNA molecule that can carry foreign DNA inside the cell and replicate it.

The cloning in a bacterial plasmid
There are 5 steps for cloning a gene:

1. Isolation of the vector and DNA of the gene to be cloned
2. Insertion of DNA into the vector: By the restriction enzyme, foreign DNA and plasmid DNA are cut off and the various fragments will melt together thanks to the adhesive ends, which will then be ligated by DNA ligase with covalent bonds.
3. Introducing the cloning vector into the cells: in some cases through the process of transformation.
4. Cell cloning
5. Identification of clones: hybridization can be used following the probe labeled with radioactive isotopes that will bind to the filaments of the desired gene, then use DNA denaturation to separate the 2 filaments.

Cloning for eukaryotes in prokaryotes
An expression vector is a cloning vector that contains the procariotic promoter necessary to obtain a cloned eukaryotic gene that functions in a prokaryotic system.
Complementary DNA (cDNA) is that DNA that is produced by reverse transcriptase of eukaryotic mRNA to subclude the incompatibility of eukaryotic DNA (full of introns) with that of procariotic target.
Artificial yeast chromosomes (YACs) are vectors that combine the essential characteristics of the eukaryotic chromosome with foreign DNA.
Electroporation occurs when an electrical impulse is applied to the cell-containing solution by which a hole is formed in the cytoplasmic membrane from which DNA enters the cell.
Eucariotic cloned gene expression is used because eukaryotic cells because many proteins are not modified after translation do not work, and prokaryotes can not modify them.

The genomic library is the set of recombined plasmids, each of which contains a particular segment of the initial genome (there is also the cDNA library).

Polymerase Chain Reaction (PCR) is a technique by which any piece of DNA can be quickly copied several times without the use of cells.
The DNA is incubated in a test tube in the presence of polymerase, nucleotides and short filaments of single-stranded synthetic DNA, and PCR thus allows to generate billions of copies of a specific segment of DNA in a few hours in a 3-cycle cycle , Where there is no need to start from a pure sample, but a small amount of DNA involved, however, PCR commits several occasional errors and therefore can not replace cloning when it takes many copies.

DNA and genomic analysis

Genomics are concerned with the analysis of whole genome sequences so that they can be used as a starting point for the study of various gene sets and their interactions.
Gel electrophoresis is a technique that allows the separation of macromolecules based on their size, electrical charge or other physical properties, it separates the macromolecules based on their migration speed on a gel placed within a field electric.
The electrophoresis divides a mixture of DNA molecules into bands, each of which is made up of DNA moleocles of the same length.

Restriction fragment analysis indirectly detects sequence differences between DNA molecules by electrophoresis on gel.
Many molecules can be identified by observing their frameworks of restriction fragments, which can be retrieved in order to obtain pure samples.

The southern blotting technique can be used to compare the DNA of different subjects.
This technique is based on the nucleic acid hybridization, and the results may show both the presence of a particular sequence in a DNA sample, but also the restriction fragments that contain that sequence.
First, restriction fragments (DNA + restriction enzyme) are prepared, then the mixture of restriction fragments of each sample is separated by electrophoresis, then blotting is used, by means of an alkaline solution the individual DNA strands remain attached to the paper, Banded, there is hybridization with the radioactive probe and finally autoradiography allows to detect the DNA bands that appear with the probe.

Restriction fragment length polymorphisms (RFLPs) are differences in DNA sequences of homologous chromosomes, which give rise to different types of restriction fragments.
The RFLP can be used as a genetic marker of a particular locus of the genome.
RFLPs are identified and studied by southern blotting, and since RFLPs are Mendelian inherited, they can be used as genetic markers to construct association maps, and the frequency with which two RFLPs are inherited together is a measure of proximity Of the 2 loci on a chromosome.

In 1980, biologist David Botstein stated that DNA variations observed in RFLP could be used as a basis for detailed mapping of the human genome.
In 1990, however, the human genome project began to map the entire human genome through the determination of the complete nucleotide sequence of DNA of each chromosome, a project developed in 3 phases:

1. Genetic Mapping: The construction of a map of association of the many thousands of genetic markers present in the chromosomes, and relying only on the microsatellite, the researchers completed a human genetic mapping with about 5000 markers.
2. Physical mapping: The distances between the markers are expressed by a physical measure (usually with the number of nucleotides), and the DNA of each chromosome is cut into a number of identifiable restriction fragments (cloned) by determining the actual order Fragments in the chromosome.
   The overlapping fragments are identified by probes using the chrmosome walking method.
   The scientists determine the order of the long fragments and then cut each of them into smaller pieces that are cloned and sorted.
3. DNA Sequencing: It is the complete nucleotide sequence of a genome that starts from the ordered DNA fragments, whose nucleotide sequence can be determined by the use of a sequencer.
   The rapid sequencing technique marks the DNA and is synthesized by the use of special nucleotides ending the chain and by the heprophoresis on high resolution gel.

In 1992, biologist Craig Venter proposed an alternative approach to the sequencing of whole genomes, proposing to skip the first two mapping phases and to go directly to sequencing through the use of powerful computers.
The human genome is in the process of being completed, but some interesting things have been discovered, such as the fact that the human genome is 85% equal to that of the mouse.

To facilitate research, the DNA sequences already analyzed are collected in electronic databases reachable by researchers around the world.
Among the various discoveries made, there is one that the human genome contains only a few genes, about 30000-40000, only 2-3 times higher than those of the fruit fly, and that solved a very small portion of human DNA is represented by genes , The remainder consists of repetitive DNA and long introns.
In addition, the comparison of genomic sequences fully confirms evolutionary links even among very distant organisms.
A typical human gene usually has at least 2 or 3 different polypeptides, using different combinations of exons.

Study of gene expression
Genome study is important for both knowing new genes and understanding how they evolve, and to understand how genes act together to create and function an organism.
By using the DNA microarray technique, small amounts of numerous single-stranded DNA fragments representing distinct genes are fixed on a slide and hybridized with different dye-labeled cDNA samples.
This technique serves to identify new genes, understand how they interact and how they work, and this technique is also used to compare cancerous tissues with healthy tissues.

Determine the functioning of the genes
To understand how a gene works, sometimes it disables and looks at differences in the body, a method is that of in vitro mutagenesis, a technique that introduces specific changes in the sequence of a cloned gene, mutations that can block the function of Protein product when it is reinserted into the cell.
With RNA interference (RNAi), genes expression is stopped by using double-stranded synthetic RNA molecules that correspond to the sequence of a particular gene to trigger the destruction of the gene-matching messenger RNA.

Proteomics is the systematic study of the whole set of proteins encoded by the genome.
The number of proins is much higher than that of genes, due to alternative splicing and post-translational modifications.
Bioinformatics is the application of computer science and mathematics to genetics and other fields of biology.
Single-nucleotide polymorphisms (SNPs) are variations of single genome-based pairs that are the cause of our genomic diversity, small diversity compared to other species.

Practical applications of DNA technology

Scientists can diagnose hundreds of human genetic disorders by engaging DNA technology through human genome study to identify disease mutations.

Gene therapy is the alteration of the genes of an individual suffering from some disease.
Cells should receive a normal allele and duplicate, however, this method has for now little success because of the brevity of the functioning of these genes.

Thanks to DNA technology, various pharmaceutical products, mainly protein, have been created, for example, insulin and growth hormone (hGH) and the tissue plasminogen activator (TPA) have been produced that helps prevent the heart attack.
The flaw of these products is that they are very expensive.
Another example of genetic product is the vaccine is an innocuous variant or a derivative of a pathogen that stimulates the immune system to fight the pathogen.
The vaccines are of 2 types: inactivated virulent viral particles and attenuated viral strain active virus particles.

DNA testing is also used in the legal field as it may lead to the identification of a criminal offense, through RFLP analysis by Southern blotting that requires fewer amounts of blood or other tissue.
DNA fingerprint, DNA fingerprint, is a specific profile of bands that can be used in the legal field, and it is recently produced using variations in the length of the satellite DNA instead of RFLPs, since these simple tandem repeats (STR ) Vary from person to person and are considered reliable.
The higher the number of DNA markers tested in a sample and the more the fingerprint of an individual is unique.
PCR is useful when DNA is of low quality or in small quantities.
Legal DNA examinations focus only on 5 small genome regions, which are known to have high variability among people, so that the possibility of having the same fingerprint is 1/100000 and 1 / a billion, depending on the Markers compared to the frequency of these markers within the population.

Another use is the environmental one, where, for example, some bacterial strains have been developed that can degrade the compounds released during oil spills at sea.

DNA technology is also used in agriculture to produce more resistant bacteria and insects, and produce more protein / vitamins.
Transgenic organisms are those organisms whose genes contain genes of other species, for example a sheep that produces better wool can be produced or a generic transgenic animal can be used as a drug factory.
The transgenic animal is generated by picking the egg cells from the receiving animal, cloning the gene from the donor animal, and implanting the egg with the gene into the recipient, which will make a transgenic offspring.
Plants are used because plant cells are easily manipulated and because it would be less expensive to produce human proteins and vaccines through plants than through classical cloning, and this is made possible because some plants are able to generate completely from a single cell.
The vector used to introduce new genes into plant cells is the plasmid Ti.

Because of various ethical issues, scientists have developed several self-control rules to prevent accidents with mutant genes that could be very dangerous by creating laboratories with very advanced security systems and generating experimental genes that can not live out of the lab.
On genetically modified organisms (organisms that have acquired one or more artificial genes) a lot has been discussed to decide whether it is ethically correct to alter nature, but its utility in fields such as agriculture or the food field is undisputed ( Animals), and some countries have decided to adopt a trademark to indicate GMOs when they are sold.

To avoid the spread of manipulated genes, researchers are also able to create them in a way that can not be transmitted, and to avoid the various risks of genetic technology, the United States has set up various control bodies, such as the Food and Drug Administration, National Institute of Health and the Department of Agriculture.
DNA technology is an important discovery, but it must be carried out with great care and caution.

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Genetics (7/8): The genome in the eukaryotes

Chromatin is formed by DNA wrapped on histones (nucleosomes) and non-histone proteins.
Chromatin changes many times during the cell cycle.

Eucariotic chromosomes contain a lot of DNA in their size, each chromosome being made up of a single double helix of DNA that contains about 2 * 108 pairs of bases in the man, if the DNA molecule is stretched it would be about 6 cm long.

Histones are responsible for the first level of DNA packing, the amount of histones in the chromatin is about equal to the amount of DNA.
Histones possess amino acids with a positive charge which is why they bind to DNA that has a negative charge.
The complex DNA-logs represent the basic structure of chromatin, and in the eukaryotes there are 5 types of histones very similar to each other.

Unplugged chromatin resembles a pearl necklace, where each pearl constitutes the nucleosome, the basic packaging unit of DNA.
The nucleosome consists of DNA wrapped around a protein core in which there are 2 molecules of each of the 4 different histones (H2A, H2B, H3 and H4), while the fifth H1 histone molecule binds to the pearl close to the chromatin Assumes the next level of packing.
Histones temporarily abandon the DNA during replication and remain united to it during transcription.
Nucleosomes by modifying their shape and position allow polymerases that synthesize RNA to move along the DNA.

Thanks to the H1 helmet, the pearl necklace can wind tightly to form a fiber of about 30 nm known as chromatin fiber 30 nm.

The 30nm chromatin fiber forms in turn the loops called loop domains acting as chromosomal scaffolds made up of non-histone proteins.

The trap domains are wrapped and folded further to form the characteristic chromosome.
If the chromatin that forms part of the chromosome is very condensed, so that it can be seen from the optical microscope, it is called etherochromatin, while the least compact one is called eucromatine.

The genome organization at the DNA level

Genes are only a small part of the genome in most pluricellular eukaryotic organisms, while repetitive DNA and other non-coding sequences represent most of the eukaryotic genome (97%), unlike prokaryotes, where most DNA Genome encodes proteins, and the nucleotide sequence encoding a prokaryotic gene proceeds from start to finish without interruption.

Repetitive DNA consists of nucleotide sequences present in multiple copies in the genome, usually not within the genes.
In mammals about 10-15% of the genome consists of repetitive tandem DNA (or satellite DNA), short sequences repeated in series (eg GTTACGTTACGTTAC ...), repetitions usually not longer than 10 pairs of bases, with densities Often different from that of the rest of the DNA.
Satellite DNA is classified into 3 types depending on the total length in each site: regular satellite DNA (100000-10milion bases), minisatellite DNA (100-100000 bases), DNA microsatellite (10-100 bases).
Much of the satellite DNA is located in centromers and telomers, suggesting that it must be implicated in structural roles and because of its position it serves to protect the chromosome from degradation or disruption that would cause the loss of coding genes, in addition tandem repetitive DNA Can stretch over several generations.
The repetitive repetitive DNA is that DNA in which repeated units are not close to each other, but dispersed in the genome.
The repetitive repetitive DNA represents about 25-40% of the genome in most mammals (and they are almost all transposon sequences) and in humans there are similar sequences of this DNA called Alu elements, the only repetitive DNA encoding.

A set of identical or very similar genes is called a multigenerational family, and these families can be considered as repetitive DNA consisting of repeated units / genes.
Multigenic families made up of identical genes usually produce RNA.
Probably the family of genes originated from a single gene due to errors during duplication of DNA.
Pseudogenes have sequences very similar to normal genes but do not generate functional products.

Except for rare mutations, the nucleotide sequence of an organism's DNA remains constant throughout its life, and when mutations in somatic cells occur, they are not transmitted to the offspring since they are not genes of gametes.

In some cases, the number of genes may temporarily increase, and the selective replication of certain genes, called genetic amplification, is a powerful means of increasing gene expression, and this can be done depending on the need to produce, for example, more Ribosome to use at the moment and then degrade.

The genomic recurrence has the remainder of long stretches of DNA that cause amplification or loss of genes.
All organisms possess transposons (10% in the human genome), DNA traits that are able to move within the genome, and when a transposon jumps into a coding gene, it can block it.
Retrotrasposons are transposable elements that move into the genome by means of intermediate RNA, a transcript of DNA retrotrasposone, where, for insertion into another site, this RNA must be reconverted by reverse transcriptase.
Alu elements are retrotrasposons that do not encode reverse transcriptase but may move using encoding enzymes from other retrograde genomes.
The permanent reorganization of DNA portions occurs in the immune system developing during cell differentiation, and this is important for the efficacy of antibodies or immunoglobulins.

Control of gene expression

Each cell of a multi-celled eukaryotic organism expresses only a small part of its genes, moreover, cells of an organism must continually turn on or turn off certain genes in response to signals coming from the internal or external environment.
Gene expression is also controlled over the long term by cell differentiation, the process where cells, through shape and function changes, specialize during the development of an organism.

Chromatin serves both to pack the DNA in a compact form so that it is in the cell nucleus, either to regulate the physical state of the DNA of a gene or adjacent region, important for determining the availability of the transcription gene , Which is also influenced by the location of the gene itself.

DNA methylation involves the addition of methyl groups (-CH3) to the DNA bases after it has been synthesized, and this would seem to be a feature of inactivity of the genes, so that if they are demethylated, they reactivate.

Histamine acetylation involves the addition of acetyl groups (-COCH3) to certain amino acid of histone proteins, and when the histones are acetylated, they change to form less closely to DNA so that the transcription proteins have a Facilitated access to acetylated genes.

The transcription
The beginning of transcription is the most important and most commonly used control point of gene expression.
Control elements are non-coding DNA segments that help regulate the transcription of a gene by binding certain proteins, transcription factors.
Transcription factors are essential for the transcription of all protein-encoding genes, and only one of these factors recognizes a DNA sequence, the TATA box within the promoter, the others recognizing proteins.
Only when the assembly of the starting complex is completed, polymerase can begin coding.
Control elements increase the efficiency of promoters through the binding of additional transcription factors.
The control elements far from the promoter are called intensifiers, which can be thousands of nucleotides away.
The activator is a transcription factor that binds to an intensifying element stimulating the transcription of a gene (similarly silencers exist).
Direct transcription control depends largely on regulatory proteins that bind selectively to DNA and other proteins, and hence a transcription factor usually has a domain of DNA binding and one for proteins.
The control elements contain sequences consisting of 4 to 10 nucleotide pairs.
The operon genes are sequentially transcribed in a single mRNA molecule and are then translated together.
The co-ordinated expression of eukaryotic genes depends on the association of a specific control element or set, with each single gene of the dispersed group.
In principle, genes that have the same control elements are triggered by the same chemical signals.

Post-transcriptional mechanisms
A cell can quickly regulate gene expression in response to environmental changes, without the alteration of the transcription.
Alternative splicing of the RNA occurs when different molecules of mRNAs are produced from the same primary transcript, depending on which RNA segments are considered exons or introns.
The phases of gene expression that can be adjusted are:

1. Adjustment of mRNA degradation: mRNAs in eukaryotes live from a few hours to a few weeks, its degradation begins with the enzymatic shortening of the poly (A) tail and this favors the removal of the cap at 5 ', digesting l MRNA from nucleases.
2. Translation Control: Most control mechanisms block the initiation phase of polypeptide synthesis when ribosomal subunits and start tRNA bind to an mRNA.
   The translation of specific mRNAs can be blocked by regulatory proteins that prevent the ribosome attack.
3. Maturation and degradation of proteins: Eucaryotic polypeptides often need to be modified to produce functional protein molecules, and regulation may take place at any of the stages of protein modification or transport.

Incorrect targeting of a protein may for example cause serious consequences such as cystic fibrosis.
Proteasomes are large protein complexes that recognize some of the proteins previously labeled and degrade because they are no longer needed for the cell.

Molecular cancer biology

Many of the mutations that cause cancer are caused by environmental influences (eg x-rays) that cause problems in regulating cell growth and division.
The genes that cause cancer are oncogenes.
Normal cellular genes, called proto-oncogens, encode proteins by stimulating normal growth and cell division.
The oncogene derives from a genetic modification leading to an increase in the amount of proto-oncogene or the growth of the activity of each protein molecule, the genetic changes that transform the proto to oncogenes are of 3 types: Inside the genome (a proto-oncogene may be close to a site that is particularly active due to chromosome breakdown, and thus increases gene transcription), amplification of a proto-oncogene (determines the increase in the number of copies of the gene in the Cell), point mutation of a proto-oncogene (modifies the protein product of the gene by producing a newer active or degradable protein).

Cancer suppressor genes are those carcinogenic genes that inhibit cell division, some repair damaged DNA, others control cell adhesion to an extracellular matrix or between them, others inhibit the cell cycle.

The product of the ras gene is a G protein that stimulates the cell cycle, and when it is produced by the ras proto-oncogene, it also activates in the absence of the growth factor.
The p53 gene works by transcription for several genes, such as p21 stopping the cell cycle, pending the activation of genes for DNA repair.
Apoptosis occurs when p53 activates suicidal genes that cause cell death when DNA damage is irreparable.
If the p53 gene is defective or absent, cancer can occur, that is, when the DNA is duplicated even if it is defective.

To produce all the characteristic changes of a tumor cell, many somatic mutations are usually needed, so the risk of cancer increases with age, because longer we live and it is more likely that it will develop due to ' Accumulation of all possible mutations.
Because a cell becomes tumorous, at least about half a dozen DNA variations must occur.
As mutant suppressor alleles are usually recessive, mutations must lead to the loss of both alleles in the cell genome to stop tumor suppression.
Most oncogenes behave as dominant alleles.
In many malignant tumors telomerase is activated, the enzyme that exposes the erosion of the extremities of the chromosome, making the tumor cell immortal.
Viruses seem to play an important role in at least 15% of cancer cases in the world, they contribute to the development of cancer by integrating their genetic material into the DNA of the infected cells.

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Genetics (6/8): From the gene to the protein

In 1909, British physician Garrod first suggested that genes determine the phenotype through the action of enzymes that catalyze specific chemical reactions in the cell, claiming that the symptoms of a hereditary illness result from the inability of an individual to produce a certain enzyme.
Another decisive proof of the hypothesis that a gene produces a specific enzyme, given by Beadle and Tatum with their studies on the mold of bread.

Not all proteins are enzymes, so it is fair to say that a gene is a polypeptide.

The genes contain the instructions for the construction of the proteins, but DNA does not produce them directly, which deals with RNA, which is chemically similar to DNA with the difference that contains ribose instead of thymine, is also constituted Almost always from a single filament.
In DNA or RNA, monomers are the four types of nucleotides that stand out for their nitrogen bases, and genes are usually made up of hundreds or thousands of nucleotides, each with a specific base sequence.
Nucleic acids and proteins contain information written in different chemical languages.
To pass DNA from the protein to the protein, two steps are required:

1. Transcription: This is the synthesis of RNA directed by DNA, where information is simply transcribed with the same language from one molecule to another.
2. A DNA strand serves as a mold for the construction of a sequence of RNA nucleotides, which is a faithful transcript of gene expression instructions for the synthesis of a protein, and this RNA is referred to as RNA messenger (mRNA).

Translation: It is the synthesis of a polypeptide under the guidance of the mRNA, where a change of language occurs and this translation occurs in ribosomes.

Transcription takes place in the nucleus and the mRNA is transferred to the cytoplasm where ribosome translation occurs.
Prior to abandoning the nucleus, the mRNA undergoes modifications before it becomes functional, in 2 stages, the pre-mRNA stage and finally the primary transcript (the final mRNA).
So recapitulating: DNA -> RNA -> protein.

There are only 4 nucleotides to specify 20 amino acids, but it has been found that the gene flow information to the protein is based on a triplet code, where genetic instructions for a polypeptide chain are written in the DNA in the form of a series of Words consisting of 3 nucleotides (thanks to which there are 64 possible coding units more than sufficient for each of the 20 amino acids).
During the transcription, the gene determines the triplet sequence within an mRNA molecule, where for each gene only one of the two DNA filaments is transcribed, and this takes the name of mold filament.
An mRNA molecule is not identical to its complementary filament where U (corresponding to T of DNA) pairs with A and C with G.
The nucleotide trunks of the mRNA are referred to as codons, which are read in the 5 'to 3' direction along the mRNA, and each codon indicates which of the 20 amino acids will be incorporated into the corresponding position of a polypeptide.
All 64 codons were decoded around the mid-1960s and it was found that each codon has specific functions or specific proteins, for example the AUG codon has a dual function, encodes the aminoacid methionine and the starting signal to the encoding process (Start codon), in addition, in an mRNA filament, the remaining 3 codons do not encode amino acids, but are stop translation signals (termination codons).
The genetic code is reminiscent but not ambiguous.
By summing up: genetic information is coded in the form of a sequence of triplet bases (codons) that do not overlap and each of which during protein synthesis is translated into a specific amino acid.
The genetic code is almost universal, with the exception of some translation systems where codons differ from normal ones, but this almost universal language has to have been functioning since the early stages of life history.

Synthesis and maturation of the RNA

RNA polymerase is an enzyme that separates the two DNA filaments and binds RNA nucleotides together, this enzyme can only add nucleotides at the 3 'end of the growing polymer so that the RNA stretches in the direction 5' -> 3 '.
The sequence of DNA to which RNA polymerase binds to the initiation of transcription is called the promoter, the sequence ending the term is called the terminator.
The promoter sequence is upstream of the terminator, and the portion of DNA that is transcribed in RNA is called a transcript unit.
Eukaryotes possess 3 types of RNA polymerases (I, II, III) and the one used for the synthesis of mRNA is II.
The promoter indicates which of the 2 filaments of DNA is used as a mold, and in the eukaryotes a group of proteins said transcription factors mediate the binding of RNA polymerase and the beginning of transcription.
Polymerase RNA may bind to the promoter only after some transcription factors are bound to it, and when both are related, it is said to be the beginning complex of the transcription.
Another crucial sequence of DNA promoter is the TATA box.
Once the polymerase is bound to the promoter DNA, the 2 filaments of DNA are performed and the enzyme begins to transcribe the mold filament.
The elongation is occurring while the RNA polymerase moves along the DNA by continuing to twist the double helix, adding nucleotides at the 3 'end of the growing RNA, the double helix of DNA regenerates and the new RNA molecule stops From his mold.
In the eukaryotes, the transcription rate is 60 nucleotides per second.
A single gene can be transcribed simultaneously by several RNA polymerase sequences that follow, and this increases the amount of transcribed mRNA.
Termination: Transcription proceeds until the polymerase RNA transcripts the sequence of a DNA terminator stopping hundreds of nucleotides after the AAUAAA signal of the pre-mRNA and at a distance of 10 to 35 nucleotides downstream of AAUAAA the pre- MRNA is cut, releasing from the enzyme.
The cutting site is also the site for the binding of a poly (A) tail.

Each end of a pre-mRNA molecule is modified, end 5 'is covered with a modified guanine, called the 5' cap which serves to protect the mRNA from degradation and is a signal of attachment to cytoplasmic ribosomes.
End 3 'is bound by a poly (A) queue that prevents RNA degradation and is also implicated in ribosome attack, and also seems to facilitate the export of mRNA from the nucleus to the cytoplasm.

RNA splicing allows to remove a large portion of the initially present RNA molecule (in the eukaryotes initially it is 8000 nucleotides, when enough is 1200).
Most eukaryotic and RNA genes possess long non-coding nucleotide sequences that are not translated.
The non-coding nucleic acid portions that lie between the coding regions are called introns, the other regions that are usually translated are called exons.
RNA polymerase transcribes DNA introns and exons, but introns are removed by splicing mRNA.
Splicing is done by short nucleotide sequences at the ends of snRNP introns, consisting of proteins and RNAs (snRNAs).
By joining the proteins they form the spliceosome, which interacts with the splicing sites by cutting the intron and joining the two extremes of the remaining exon.

Ribozymes are introns RNA molecules with enzymatic activity that allow to catalyze their removal.

Introns are important because they contain sequences that control gene activity and have discontinuous genes (composed of introns and exons) to encode more than one type of polypeptide.
Alternative splicing of the RNA is when some genes give rise to 2 or more different polypeptides, depending on which portions are treated as exons during the maturation of the RNA.
This splicing may be why men are so diverse, though having a very low genetic kit, just twice that of the fruit fly.
Domains are those regions of structurally and functionally distinct proteins born through discontinuous genes, and exons different encode different domains of a protein.
Introns increase the chances of increasing cross-over-crossing.

The synthesis of proteins

The translation interpreter is the RNA transfer (tRNA) that transfers amino acids from the cytoplasmic to the ribosomal pool, which adds these amino acids to the polypeptide chain extension end.The tRNAs are not all equal when one of them reaches the ribosome, carries a specific amino acid bound to one end, while at the other end there is a triplet of said anti-codon nucleotides, which appears on a complementary codon of the mRNA.The genetic message is then translated into a codon after the other as the tRNAs carry the amino acids in the expected order and these are linked by forming a ribosome chain.In the eukaryotes the tRNA is produced within the nucleus of the cell and must be transferred to the cytoplasm, and each molecule of it is formed by a single 80 nucleotide RNA filament that folds onto itself forming a molecule with a three-dimensional structure L form, where at one end there is the anticodone and at the other end there is the 3 'end, the linking site of the amino acid.There are about 45 tRNA molecules, some of which possess anticodies that recognize 2 or more different codons.The oscillation is the least rigid of anti-coding rules, and it explains why different codons that encode the same amino acid differ only in their third base (that is, the third U base of the tRNA can fit, for example, with A or G of the mRNA ).Anti-conjunction codon binding must be preceded by a proper coupling between the tRNA and its amino acid, and this bond is made by the amino acid-tRNA synthase enzyme, of which there are 20, each for each amino acid.Ribosomes favor the coupling between tRNA antibodies and mRNA codons during protein synthesis.The ribosome consists of 2 subunits, the major subunit and the lower subunit, both constituting ribosomal RNA (rRNA), which constitutes 2/3 of the mass of a ribosome.The ribosome has 3 mRNA binding sites: the P site links the tRNA that carries the chain into growth, site A links the tRNA carrying the amino acid that needs to be added to the chain, site E is where free tRNAs abandon The ribosome.The ribosome holds close tRNA and mRNA and positions the new amino acid by adding it to the carboxylic acid end of the nascent polypeptide.The synthesis of a polypeptide chain consists of 3 phases: start, elongation, termination.Beginning and elongation need energy consumption supplied by GTP hydrolysis.The initiation involves the association of the tRNA mRNA carrying the first amino acid of the polypeptide and the 2 ribosome subunits.In the elongation, amino acids are added one at a time to the previous amino acid, and occur in a 3-cycle cycle: codon recognition, peptide bond formation, transfer.Termination is the last stage of the translation where the elongation continues until it finds a stop codon (triplet UAA, UAG and UGA) in the ribosome site A of the mRNA, and then site A binds to one Protein said release factor which involves the polypeptide hydrolysis at Site P, causing its release from the ribosome.

An mRNA molecule is usually used to produce several simultaneous copies of a polypeptide, thanks to several ribosomes that operate simultaneously.
When a ribosome moves beyond the start codon, another ribosome may bind to the mRNA, and so on, forming a polybosomal, a structure that speeds up the production of polypeptides.

After the synthesis, the polypeptide begins to wind up to reach the proper structural shape for its functioning, conformation determined by the primary structure, in turn determined by the gene.
The chaperone protein favors the proper folding of the polypeptide so that it is a functional protein, while the phenomenon of denaturation is when the protein loses its shape and becomes inactive.

There are 2 types of ribosomes, free ribosomes and ribosomes bound.
The free radicals are suspended in the cytosol and synthesize soluble proteins that will function in the cytosol, the bound ones being attached to the wrinkled endoplasmic reticulum ERr and produce proteins for internal membrane systems and proteins that can be exported out of the cell.
Free and bound ribosomes are identical and can be exchanged for space.
The synthesis of all proteins begins in the cytosol and terminates them, unless the nascent peptide pushes ribosome to bind to ER.
The polypeptides for membrane systems therefore have a signal peptide that directs them towards the ER.
The signal recognition particle (SRP) promotes the link between the ribosome and the receptor membrane protein of the ER, where it resumes synthesis and removes the signal peptide.


Types of eukaryotic RNAs

RNA messenger mRNA	Carries information from DNA to ribosomes
RNA transfer tRNA	It transduces the codons of the mRNA into amino acids
RNA ribosomal rRNA	It performs catalytic and functional roles within ribosomes
Primary transcript (eg pre-mRNA)	It is a precursor to mRNA, rRNA and tRNA
Small SNRNA nuclear RNA	It has structural and catalytic roles in spliceosomes
SRP RNA	Complex of RNA and proteins that recognizes the peptizes signal of polypeptides directed towards ER

Point mutations
Mutations are genetic material modifications, point mutations are chemical modifications charged by a single pair of bases of a gene.
If a point mutation occurs in a gamete, this can be transmitted to the progeny, and if mutation has an effect on the phenotype, it is termed hereditary disease.
Point mutations can be divided into 2 categories: base pairs substitutions and base pair insertions or deletions.

Replacements consist of replacing a nucleotide and its partner on the complementary filament with another pair of nucleotides.
A variation of a pair of bases can transform a codon into another that is translated from the same amino acid by making a silent mutation, or not affecting the protein's functioning, while other substitutions may involve amino acid substitution but will not affect the Same function of the protein.
In other cases, amino acid substitutions involve modifying protein functions, in some cases creating new functionalities, while others may damage their normal functioning.
Replacements are usually sense mutations (missense), that is when the modified codon still encodes an amino acid and therefore has a meaning, not necessarily correct, instead the substitutions that make a stop signal are referred to as nonsense mutations and almost All lead to the production of non-functional proteins.

Intakes and deletions are mutations where the nucleotide pair is added or lost, and are dysfunctional mutations because they can alter the reading grid in the said shift grid shift mutation phenomenon (Frameshift mutation), which will occur each time the number of nucleotides is not multiple of 3, and unless this shift takes place at the end of the gene, it will produce a protein almost unworkable.

Other errors can occur through spontaneous mutations, mutations involving large DNA fragments.
Mutagens are physical and chemical agents that interact with DNA causing mutation.
They can be X-rays, ultraviolet light, and may impersonate improperly during DNA replication, or replicate the DNA by inserting inside it and forming a twin helix distortion, while others modify the bases chemically, altering the 'pairing.
Much of the carcinogens are mutagenic and most mutagens are carcinogenic.

The gene may have different definitions, can be considered a hereditary unit that can envision a phenotypic character, may be the locus synonym, can be a portion of a specific nucleotide sequence along a DNA molecule.
It can be said that a gene is a region of DNA whose end product is a polypeptide or a RNA molecule.

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Genetics (5/8): The Molecular Fundamentals of Heredity

After Morgan's discovery, many tried to determine if DNA or proteins, the genetic material of chromosomes.
In 1928 Griffith studied the bacteria and discovered the phenomenon of transformation, a variation of the genotype and phenotype linked to the assimilation of foreign DNA by a cell.
Avery in 1944 claimed that the transformed agent was DNA, but his discovery was met with skepticism, as many believed that proteins were the genetic material of excellence.
In 1952, Hershey and Chase studying bacteriophages claimed that DNA was the genetic material of the T2 bacterium, which was capable of reprogramming the cell to make it produce other viruses, and experimented with their theory by using radiotomized isotopes to mark DNA, Demonstrating that proteins did not come into play in this genetic transmission process.
Other tests are related to DNA distribution during mitosis, and Chargaff in 1947 demonstrated the DNA composition (the nitrogen base is always equal cmq: Adenina A, Timina T, Guanina G, Citosina C) ranges from one species to another .
Moreover, Chargaff discovered the equalities A = T and G = C common to all DNA molecules, now known as Chargaff's rules.
The final test was given by Watson and Crick who discovered in 1953 the double-helix DNA structure thanks to X-ray crystallography by the scholar Rosalind Franklin.
These scholars discovered that the DNA propeller runs a full turn every 3.4nm in terms of its length, and that the nitrogen bases were pegged so that adenine was with quinine and guanine with cytosine.
Adenine and guanine are purines, nitrogenous bases with 2 organic rings, while cytosine and thymine are pyrimidines, single-ring bases.
Hence adenine forms 2 hydrogen bonds only with thymine and guanine forms 3 hydrogen bonds only with cytosine.
The amount of guanine is thus equal to that of cytosine and adenine to thymine, and the linear sequence of the 4 bases can be varied infinitely, and each gene has a single order or sequence of bases.

Replication and DNA repair

The semiconservative model of Watson and Crick predicts that when the double helix is ​​duplicated, each of the daughters molecules is part of the old parent molecule and a new part.
Each of the human cells has about 6 billion pairs of bases, although a cell takes a few hours to copy all of its DNA and this replication is performed with very few errors, about one every billion nucleotides.

DNA replication begins at sites of said replication origins, where proteins bind to DNA by separating the two filaments and opening a replication bubble.
Replication proceeds in both directions until the entire molecule is copied.
At the end of a replication bubble there is a replenishing force, a Y-shaped region where new DNA filaments stretch.
This elongation is catalyzed by DNA polymerase enzymes that binds the nucleotides paired to the base at the expanding end of the new filament at a rate of about 50 nucleotides per second in human cells.
Polymerase DNA adds nucleotides in the free end of an increasing DNA strand but not in the 5 'end and therefore a new DNA strand may stretch only in the 5' to 3 'direction.
The polymerase positions itself in the molding force of a mold filament and continuously adds nucleotides to the complementary filament as the force extends and the filament formed with this mechanism is referred to as the filament guide.
To lengthen the other new filament, the polymerase must work on the other mold in the direction away from the force, and the DNA synthesized in this direction is referred to as a delayed filament.
The polymerase molecule moves away from the replication bubble when it opens, and replicates a short segment of DNA.
The delayed filament is initially synthesized as a set of short segments called Okazaki fragments.
The DNA ligase enzyme joins the sugar-phosphate skeletons of Okazaki fragments to generate a single DNA strand.
Polymerase DNA can not initiate the synthesis of a polynucleotide filament, it can only add nucleotides at the 3 'end of a pre-existing filament. The trigger is represented by a short section of RNA synthesized by primary enzyme, and each trigger is eventually replaced by DNA.
Instead, in the delayed filament each single fragment of Okazaki must be triggered and these triggers are converted into DNA before the ligase unites the fragments together.
The helix is ​​an enzyme that performs the double propeller at the level of the replication force, separating the two filaments.
The protein that binds single-stranded DNA aligns along stranded DNA filaments, keeping them separate, while they work as molds for the synthesis of new complementary filaments.

Enzymes that control and correct errors in DNA replication
Errors in initial wrap between new nucleotides and mold filaments are quite frequent.
Polymerase itself checks for errors during replication, when it finds an improperly padded nucleotide, removes and resumes synthesis.
For repairing improper use of polymers, the cells use special enzymes that recognize and correct inappropriate paired nucleotides.
Nuclease is the enzyme that removes the damaged portion, then replaced by other nucleotides, thanks to the polymerase and the ligase, in a process called nucleotide excision repair.
Hereditary xeroderma pigmentous disease is caused by a deficiency of an enzyme involved in excision repair, and causes hypersensitivity to light and skin cancers.
In principle, most of the repair processes involve DNA molecule polymerase activity.
Normal DNA replication does not allow to complete the 5 'end, and therefore repeated replication cycles would lead to the production of ever-shorter DNA molecules.
Telomers are special nucleotide sequences, TTAGGGG, which do not contain genes.
Telomeric DNA protects the genes of the organism from erosion and prevents the extremities from activating cellular systems to monitor DNA damage.
Telomerase is a particular enzyme that allows to restore shortened telomers, catalyzing their elongation, thanks to an RNA molecule that acts as a mold for the new segments of the telomer at the 3 'end.
Telomerase is not present in most pluricellular cells, and therefore in somatic cells DNA tends to be shorter in elderly cells.
Thus, telomeres are likely to be the cause of the life-span of organisms.
Telomerase is present in the germ cells that give origin to the pegs and is therefore present in the infants.
Unfortunately telomerase keeps cancer cells alive by not shortening the telomeres.

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