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Wong_Katrina_Block5_MM9 (non mendelian genetics: (degree of dominance,…
Wong_Katrina_Block5_MM9
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non mendelian genetics:
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- Polygenic traits displays a bell curve distribution
- Nondisjunction of homologous chromosomes during gamete formation
- Males hemizygosity for sex-linked genes
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- inheritance of mitochondrial DNA
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sex linked genes
in ovaries and testes, 2 sex chromosomes segregate during meiosis. each ovum has one X. half of a male's sperm are X, half are Y
sex linked gene: a gene located on either sex chromosome. fathers pass sex linked alleles to all daughters, mothers pass to both sons and daughters
if a sex linked trait is due to a recessive allele, female will only express the phenotype if she's a homozygote. since males only have one locus, homozygous and heterozygous lack meaning...hemizygous. therefore, any male receiving the recessive allele from mom will express it
though female mammals inherit 2 X, one X becomes inactive during embryonic development... cells of females and males have the same amount of genes w loci on the X chromosome
the inactive X becomes a barr body which lies iinside the nuclear envelope. barr body chromosomes are sometimes reactivated in the cells that give rise to ova, so every female gamete has an active X
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