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Unformatted text preview: CHAPTER 11 INHERITANCE AND CHROMOSOMES Linked genes do not assort independently Thomas Hunt Morgan studied fruit flies o Demonstrated that genes are arranged in a linear order on each chromosome o Independent assortment does not apply if the two loci lie close together in the same pair of homologous chromosomes Linked genes tend to be inherited together Linkage is the tendency for a group of genes on the same chromosome to be inherited together in successive generations o Heterozygous individuals were crossed with homozygous recessive individuals Two-point test cross Experiment o If genes were unlinked, four gametes would be produced with equal chances BV, Bv, bV, bv Bv and bV would be recombinant types because they form two new gametes (not present in parents) BV and bv would be parental types because they form the gametes formed by the parents o Normally each would be equally likely, but because they are linked, parental types are much more common Calculating the frequency of crossing-over reveals the linear order of linked genes on a chromosome By calculating how often recombinant types occur, we can calculate how far away two alleles are from each other on a chromosome Sex is generally determined by sex chromosomes Major sex-determining genes are carried by sex chromosomes o Females have two...
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- Fall '08