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HHMI BioInteractive: X Inactivation

by Pearson
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SPEAKER: And the cells start off in a female with 2 X chromosomes. The cell divides and the embryo is getting slightly bigger and still, each cell has both X chromosomes active. But in early embryogenesis, each cell will inactivate activity one of its Xs. And one cell will remain with the paternal X as active while the other one the maternal one. And now, this process will happen at random. And you'll have almost half of the cells with the maternal X active, half with the paternal X. The embryo will continue to grow, cells divide. All the descendants of that cell-- all the descendants will keep the same X active. And you've seen this in calico cats, right? The coat color gene is on the X chromosome. And that's precisely why these cats look like this, a mosaic appearance, because of the process of X chromosome inactivation.
SPEAKER: And the cells start off in a female with 2 X chromosomes. The cell divides and the embryo is getting slightly bigger and still, each cell has both X chromosomes active. But in early embryogenesis, each cell will inactivate activity one of its Xs. And one cell will remain with the paternal X as active while the other one the maternal one. And now, this process will happen at random. And you'll have almost half of the cells with the maternal X active, half with the paternal X. The embryo will continue to grow, cells divide. All the descendants of that cell-- all the descendants will keep the same X active. And you've seen this in calico cats, right? The coat color gene is on the X chromosome. And that's precisely why these cats look like this, a mosaic appearance, because of the process of X chromosome inactivation.