Lecture 6 - Lecture 6 When we talk about gene position the...

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Lecture 6 When we talk about gene position the term locus is used to designate the chromosomal location of a gene. What we are going to do is to map genes relative to one another. To begin, we need two genes on the same chromosome. Last lecture we saw how you could tell whether a gene is on the X chromosome by how alleles of the gene are inherited differently by males and females. Consider two mutations on the X chromosome of Drosophila; crossveinless and white eye. Genotype Phenotype Xcv+w+ Y wild type Xcv- w+ Y crossveinless wings Xcv+w- Y white eye Xcv-w+ Y x Xcv+w-Xcv+w- (true breeding) All of the daughters from this cross will have two different X-chromosomes, which differ at two loci: Xcv+w-Xcv-w+ We want to follow these X chromosomes into the next generation so after a cross we look at male flies. parental classes: Xcv+w-Y and Xcv-w+Y and crossover classes: Xcv-w-Y and Xcv+w+Y (crossveinless, white) (wild type) In the crossover classes the alleles appear to have separated and moved from one X to the other. Genes on the same chromosome often do not assort independently. Such behavior is known as Linkage . unlinked — crossover classes appear at same
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This note was uploaded on 01/20/2012 for the course GENETICS 380 taught by Professor Glodowski during the Fall '08 term at Rutgers.

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Lecture 6 - Lecture 6 When we talk about gene position the...

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