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How we know there is a heritability? Part 1

When we try to understand genetic diseases, we see that they often do not follow a single mode of inheritance.
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The genetics of complex traits is the real issue of the genetics, let’s say that genetics of the Mendelian traits is interesting but does not account for most of the interesting things we want to deal in humans and we have to understand not only the cases for which we have nice models, but the cases that we not even understand properly. So here today we are going to see how it works the genetics of complex traits, how we know that a given trait is transmitted, there is a heritability, the meaning that it runs in family because of genes, how today lots of geneticist are working on that and how this kind of work is going to be done in the future.
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When we try to understand genetic diseases, we have to see that in many cases there are complex diseases that do not follow the rules of Mendel’s law, that do not follow single ways of inheritance. We can think on many cases of diseases or traits or whatever and we see that they run in families, they have to be in a certain way inherited, but they do not follow a single model of inheritance that would follow diseases and that would follow the molecular view of our genome. In general, complex diseases, and this is the most important thing, is that they have high prevalence- they affect lots of people.
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And here we have cases of arthritis, we have lots of different autoimmune disease, all the psychiatric diseases, autism, schizophrenia, bipolar disorders; cancer… there is a genetic base in cancer and in most cases, there is also a complex susceptibility to it; we have the cardiopathies; meaning that we have lots of cases, diabetes for example, in which it’s extremely interesting, that they have a relevant genetic component, no simple model of inheritance, and we have in all the cases several genes with small contributions. We are not going to talk on the gene for (a given disease) as we did for example for cystic fibrosis but genes of susceptibility to schizophrenia for example.
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There are multiple alleles interacting among them, interacting with the environment and these complex interactions are at the base of the genetic of complex diseases.

When we try to understand genetic diseases, we see that they often do not follow a single mode of inheritance.

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