Biology Chapter 15

Biology Chapter 15 - I chromosomes

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I. Chromosome Theory of Inheritance - Several researchers proposed in the early 1900s that genes are located on  chromosomes. - The behavior of chromosomes during meiosis was said to account for  Mendel’s laws of segregation and independent assortment. - The chromosome theory of inheritance states that Mendelian genes have  specific loci on chromosomes.  - Chromosomes undergo segregation and independent assortment. - Thomas Hunt Morgan provided convincing evidence that chromosomes  are the location of Mendel’s heritable factors. A. Morgan’s Choice of Experimental Organism -  Morgan worked with fruit flies because a) They breed at a high rate. b) A new generation can be bred every two weeks. c) They have only four pairs of chromosomes. - Morgan first observed and noted wild type, or normal, phenotypes that  were common in the fly populations. - Traits alternative to the wild type are called mutant phenotypes. B. Correlating Behavior of a Gene’s Alleles with Behavior of a Chromosome Pair - In one experiment Morgan mated male flies with white eyes (mutant) with  female flies with red eyes (wild type). - The F generation all had red eyes. - The F generation showed the 3:1 red:white eye ratio, but only males had  white eyes. - Morgan determined that the white-eye mutant allele must be located on the  X chromosome. - Morgan’s discovery that transmission of the X chromosome in fruit flies  correlates with inheritance of the eye-color trait was the first solid evidence  indicating that a specific gene is associated with a specific chromosome. II. Gene Linkage - Linked genes tend to be inherited together because they are located near  each other on the same chromosome. -
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This note was uploaded on 11/22/2010 for the course BIOLOGY 101 taught by Professor None during the Spring '10 term at Kent State.

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Biology Chapter 15 - I chromosomes

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