The Chromosomal Basis of Inheritance

The Chromosomal Basis of Inheritance - THE CHROMOSOMAL...

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THE CHROMOSOMAL BASIS OF INHERITANCE Linked genes o Alleles of loci that are on the same pair of homologous chromosomes – do not undergo independent assortment Two-point test cross o Most sensitive test for linkage o F1 individuals (heterozygous at both loci - are crossed with double homozygous recessive individuals o AaBb x aabb o Linkage in Fruit Flies (Drosophila) Notation B = normal gray body (wild type) B = black body V = normal long wing (wild type) V = vestigial (short) wing P generation was: o BBVV and bbvv Two point cross AaBb x aabb AB Ab aB ab ab AaBb Aabb aaBb aabb 45 5 4 46 Linked 5 rec 45 par 46 par 4 rec 45 par 5 rec 4 rec 46 par 26 23 24 27 unlinked Sex determination o Mechanisms actually vary o Not all organisms with separate sexes have sex chromosomes Sex chromosomes o Humans and Drosophila XX = female XY = male o Birds ZZ = male ZX (or sometimes Z0) = female Discovery of X-linkage o Drosophila o Laboratory of Dr. Thomas Hunt Morgan (at Columbia University)
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This note was uploaded on 02/28/2009 for the course BIOLOGY 101 taught by Professor Martin during the Fall '08 term at Rutgers.

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The Chromosomal Basis of Inheritance - THE CHROMOSOMAL...

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