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The basics of genetics, how does it work? Part 3

Mendel gave the answer to how a single gene is at the base of a genetic trait and how a trait goes from one generation to the next.
In general, when we see in humans, when we talk on Mendel laws, we talk many times on disease. The idea is that there are in humans many genetic diseases that are caused by a single variant that produce a change that disrupts the function of the proteins. In general, these are very rare diseases that are caused by variants that are very, very low frequency and are in general recessive.
They are originated by a mutation and are being transmitted along the generations mainly if they are recessive because the carriers do not present all the characteristics and in this case, it may be hidden in the population and suddenly appears, reappears when they encounter a couple that both of them have this… both are carriers and then the recessive are being being found in both of them. In general, are being transmitted but of course in some cases may have been produced de novo, meaning (new) in that specific variation.
Victor McKusick was a person that was really worried about genetic diseases in humans and he began publishing a book very well-known on Mendelian Inheritance in Man that today has been posted as a web page called OMIM. If you have any doubt of a given trait, given characteristic that may have a way of transmitting, that may be genetic, go to this webpage and you have the answer because this is being updated.
For example, the cases in which we know quite a lot: cystic fibrosis a recessive very, very frequent or relatively frequent in Europeans; we have phenylketonuria which is also very interesting because depending on the diet people will be near, will be normal or will have really strong problems and these in western countries are being analyzed at birth; or the Tay-Sachs disease that is extremely severe and this has been under surveillance mostly among Ashkenazi Jews because they have a much higher frequency than other populations. These diseases, in general they have a very small frequencies that are very strange but hey have a very strong deleterious effect. Why we mostly see mutations as causing disease? The idea is very simple.
A mutation is a change that affects the function of our body and, in general, if we make a random change in any of the components on ourselves –as we if we did that in the computer– the possibilities of getting something worse are much higher than improving it. In general, these rare diseases are due to mutations that these mutations in most cases produce diseases that are being reduced by natural selection and relatively increased by selection. If you are interested in these rare diseases, there’s this interesting Orphanet webpage but the genetic impact is interesting, but the medical impact is very important in the sense that for each of them because each of them is different and there are thousands.
Each of them is different and each of them needs a strong work to workout possibilities of therapies and drugs and this is something that most companies do not put much effort because of the low number of individuals having that.

Mendel gave the answer to how a single gene is at the base of a genetic trait and how a trait goes from one generation to the next.

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