b112_lec15 - BIOL 112 BIOL112 Lecture15...

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BIOL 112 Campbell, Chapter 15, Chromosomes & Inheritance 1 BIOL 112 Lecture 15 Recombination of Unlinked Genes: Independent Assortment of Chromosomes The Fruit Fly: Model Genetic Organism Advantages of Drosophila Prolific breeders. Produce numerous offspring. Can be bred every two weeks Can be bred every two weeks. Only 4 sets of chromosomes (1 set = sex chromosomes). Easy to sex under a dissecting scope. The Meaning of Linkage Linked loci are located on the same chromosome. Chromosomes are distributed as units during meiosis so linked loci will not assort independently. Note that the phenotypic ratio in a dihybrid cross with complete linkage is 3:1 and not the typical 9:3:3:1 All of the loci on a particular chromosome are referred to as a linkage group .
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BIOL 112 Campbell, Chapter 15, Chromosomes & Inheritance 2 Crossing Over Chromosome Mapping By performing numerous crosses geneticists can determine which loci are on which chromosomes. Based on crossover values they can also tell the order in which the genes occur and approximately how far apart they are. These data can then be compiled to form a chromosome map . Chromosome Mapping A 1% crossover value is set equal to one map unit . The further apart a pair of loci are the more
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This note was uploaded on 06/18/2009 for the course BIOL- 112 taught by Professor Bryanness during the Fall '09 term at Pacific Union.

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b112_lec15 - BIOL 112 BIOL112 Lecture15...

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