biol lec 5

biol lec 5 - Two ways of getting recombinant gametes...

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Two ways of getting recombinant gametes · Through independent assortment If genes are unlinked · Through process of crossing over If genes are incompletely linked · Crossing over between 2 genes happens more often when genes are further apart Sex linked genes · Genes that are present on sex chromosomes (X or Y) -different shapes (heteromorphic) -act homologous during meiosis -have pseudoautosomal regions that allow chromosomes to pair during prophase · Autosomes (non- sex chromosomes)èhomomorphic Humans · Heterogametic sex: (XY) males · Homogametic sex: (XX) females · Chicken butterflies and fish are switched Heterogametic sex: (ZW) Homogametic sex: (ZZ) Sex-linkage · X chromosome -in most species, contains as many genes as an autosome of similar size -genes are “X-linked” or “Sex-linked” -a matter of geography: not function · Y chromosome -contains very few genes (300-1300 on X) -genes are “Y-linked” or “sex-linked” A matter of geography, not function Inheritance of sex chromosomes · XX x XYà XX x from mom and x from dad XY x from mom and y from dad -not homozygous or heterozygous Hemizygous- only 1 copy of any sex-linked gene All alleles are expressed (recessive alleles cannot be masked)
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biol lec 5 - Two ways of getting recombinant gametes...

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