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Genetics - VA Biology SOL
Genetics - VA Biology SOL

... ears?  Can you raise just one eyebrow? ...
Homologous chromosome
Homologous chromosome

... SOURCE: BIOLOGY: CONCEPTS AND CONNECTIONS BY CAMPBELL, REECE, MITCHELL, TAYLOR ...
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Genetic Terms - Ask Doctor Clarke

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... Only one of the X chromosomes is fully active in most mammalian female somatic cells. The other X chromosome is condensed into a Barr body located inside the nuclear membrane. This means that both males and females have an equal dosage of X chromosome genes. - Females don’t have twice the amount of ...
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The allele for brown eyes is dominant over that for blue eyes. Would

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Sexual Reproduction and Inherited Traits
Sexual Reproduction and Inherited Traits

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GeneticsNotes08
GeneticsNotes08

... •_____________________________ express all of their sex linked genes. • Expression of the disorder depends on which parent ____________ the allele and the __________ of the ...
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Skewed X-inactivation

Skewed X chromosome inactivation occurs when the inactivation of one X chromosome is favored over the other, leading to an uneven number of cells with each chromosome inactivated. It is usually defined as one allele being found on the active X chromosome in over 75% of cells, and extreme skewing is when over 90% of cells have inactivated the same X chromosome. It can be caused by primary nonrandom inactivation, either by chance due to a small cell pool or directed by genes, or caused by secondary nonrandom inactivation, which occurs by selection. Most females will have some levels of skewing. It is relatively common in adult females; around 35% of women have skewed ratio over 70:30, and 7% of women have an extreme skewed ratio of over 90:10. This is of medical significance due to the potential for the expression of disease genes present on the X chromosome that are normally not expressed due to random X inactivation. X chromosome inactivation occurs in females to provide dosage compensation between the sexes. If females kept both X chromosomes active they would have twice the number of active X genes than males, who only have one copy of the X chromosome. At approximately the time of implantation (see Implantation (human embryo), one of the two X chromosomes is randomly selected for inactivation. The cell undergoes transcriptional and epigenetic changes to ensure this inactivation is permanent. All progeny from these initial cells will maintain the inactivation of the same chromosome, resulting in a mosaic pattern of cells in females.
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