Seminario 14 Cromosomas sexuales y herencia - Rodolfo Rey

Continuing with the patterns of classical inheritance, my name is Rodolfo Rey, and in this seminar we're going to look at sex chromosomes and inheritance, X-linked inactivation, and X-linked and Y-linked inheritance. To that end, the lesson plan will begin with a review of sex chromosomes, followed by the behavior of sex chromosomes during mitosis and

meiosis, which you should have already covered in cell biology. And we're going to address what X chromosome inactivation is, and then X-linked inheritance. Reviewing the sex chromosomes, we all have 23 pairs of chromosomes, of which 22 pairs are autosomes. And the sex pair, which in general in the male is Xi and in the female

is XX, but there may be exceptions. What are these sex chromosomes like? Well, unlike autosomes where the two homologous chromosomes are identical, in the case of sex chromosomes, the X chromosome is much larger and has many more genes than the I chromosome. The X chromosome has approximately 164 megabases compared to only 60 megabases for the I chromosome. That is, the

I chromosome is approximately three times smaller than the X chromosome. And just look at the number of genes on the X chromosome: 867 compared to only 55 on the I chromosome. What other differences do these chromosomes of the sex pair have with autosomes? And that is because the autosomes, as we remember during meiosis,

cross over their sister chromatids and there is a mating that allows the exchange of genetic material. That can happen in autosomes, anywhere in the autosomes. In sex chromosomes, this pairing can only occur in regions called pseudoautosomal. E are called pseudoautosomal, there are two of them. One is the pseudoautosomal one, which is at the