Biology 1001A Lecture Notes - Lecture 15: X-Inactivation, Nucleosome, Calico
9 Apr 2016
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Reading secion 14. 2d on chromain remodelling, note fig. Idenify role of histones in dna packaging and expression. Human females have twice as many copies of genes carried in the x chromosomes as males. Which chromosome becomes inacive is random, and happens during embryonic development. Once a x chromosome is inacivated, all same x chromosomes in the daughter cells are also inacivated. Sill this random inacivaion afects the enire body litle when it comes to recessive sex-linked diseases, because the dominant allele is acive enough in the important cells. Sill, someimes the inacivaion causes very diferent efects. Example calico males are either black or orange, but because of the inacivaion of x chromosomes in certain regions of female calicos, they are orange and black. So this is not an example of co-dominance. There is a dominant allele but it doesn"t repress the recessive in some areas because of the random x inacivaion.
