Class 7 - Gene interactions and effects on inheritance

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Gene interactions and effects on inheritance http://www.doctorzebra.com/prez/g01.htm COULD THE “FATHER OF OUR COUNTRY” HAVE BEEN KLINEFELTER (XXY)? OR JUST TALL, INFERTILE, AND LACKING FACIAL HAIR?
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Dosage compensation What is it? To cope with the problem of twice the number of x-linked genes in females compared to males, the expression of those genes is regulated differently in each sex This is effected in a variety of ways
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X-inactivation in mammals X X X X embryo + fertilization X X X X X X X X X X X X X X X Two weeks old embryo 500-1000 cells Each inactivates one X The choice of inactivating the male- derived or femail- derived X is random X o o X X o X o o X X o o X X INACTIVATION IS MAINTAINED “CLONALLY” WITHIN EACH FEMALE REACTIVATION OF INACTIVE X OCCURS PRIOR TO MEIOSIS
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At the cellular level RANDOM X INACTIVATION BARR BODIES PATCHES ARE RESULT OF CLONES OF X- INACTIVE CELLS
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X-linked Colorblindness X CB - Normal vision X cb - Color blind In a X CB X cb female: if X cb inactivated -> normal vision if X CB inactivated -> color-blind In reality, females are mosiacs of two cell types in each eye leads to partial color vision in heterozygous females
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X inactivation n-1 rule cells appear to be able to “count” X chromosomes no matter how many X chromosomes are present in a cell all but one will be inactivated specifc DNA sequences in the X inactivation center appear to be involved
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If X inactivation in humans shuts down extra X chromosomes, why do XXY and XXX individuals show any phenotypic effects? A. X inactivation can only shut down one X per cell.
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Class 7 - Gene interactions and effects on inheritance

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