Biology - Genetics 3
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chromosome composition, the number and appearance of chromosomes in the nucleus.
- Described short hand by Total#Chromo,SexChromo,Mutations.
- Ex. Female with Down Syndrom:
- trisomy-21, three copies of chromosome 21.
- 1 in 800 births
- caused by nondisjunction event during meiosis (either parent, mostly female), or during early mitosis (embryogenesis).
- results in mental issues (too many DYRK proteins) and heart defects
having three copies of one chromosome (2n+1)
having three entire chromosome sets (3x)
XYY & XXX
- completely harmeless
- with the extra Y you have so few genes on the Y chromosome
- with the extra X you simply have two inactivated X chromosomes instead of just 1
- only viable monosomy in humans is the 45,X, aka Turner Syndrome
- female because of lack of Y chromosome. Only viable because normally one X chromosome is inactivated anyways.
- usually results in shorter than average, infertile, and often heart issues in people. These issues come from the lack of the psudoautosomal region in inactivated X chromosomes
genes found on both the X and Y chromosome which escape X chromosome inactivation
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