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Chapter 11

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BIOL 1000
Angelo Belcastro

CHAPTER 11 Genetic Linkage/Recombination Linked genes  Genes located on the same chromosome may be inherited together in genetic crosses Linkage/Recombination in Drosophilia  Fruit fly  Reasoned genes located far apart on chromosome more likely to be separated from each other during meiosis Recombination Frequency Used to Map Chromosomes Sex Linked Genes  Genes located on a sex chromosome  Females have two copies of XX chromosomes  Males only have one X, and one Y chromosomes Sex Determination and SRY Gene  Directs development of “maleness” in early development of embryo  Becomes active after 6-8weeks in XY embryos  Produce proteins that stimulated the development of testes o Testes then secrete hormones that start the degeneration of tissue that would turn into female parts  XX embryos DONT have SRY gene  Genes coding breast development, facial hair coded in autosomes  Females inherit genes for penis structure, but do not express them  Sex linkage comes from two differences o Males have one X, hence are hemizygous for genes located on X chromosome o Females have no alleles located in the Y chromosome  Fly: white eye allele located on X chromosome Inactivation of X chromosome  Females inactivate most of the genes on one X chromosome  Is a condensation process o Folds and packs chromatin of one of the two chromosomes into a tightly coiled state, Barr Body o Occurs during embryonic development o Same X is inactivated in all the descendants of the cell Chromosome Alternations Affecting Inheritance  Deletion: broken segment lost from chromosome  Duplication: if segment is broken from one chromosome and inserted into its homologous one. That chromosome now has two of the same o Cri du chat o May be beneficial or detrimental o
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