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Gene Mapping

Gene Mapping

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Gene Mapping

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  1. Gene Mapping

  2. Human Genes Mapped • http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/chooser.shtml • Two different ways of mapping • Breeding Experiment • Modern molecular techniques

  3. Linked Genes and Crossing Over

  4. Tetrads

  5. Crossing Over • Crossing over allows for great genetic diversity because it allows typically linked traits to recombine. • Recombination = the process of forming new phenotypes in offspring by crossing over • New phenotypes appear in a small percent of the F2 generation:

  6. Recombination Holds the Key to Gene Mapping! • Gene farther apart from each other on a chromosome are more likely to cross over. • Mapping Units = m.u. • Not a physical measurement • Measures the frequency of recombination • If recombination occurs in 5% of the F2 generation, the two genes are 5 m.u. apart

  7. Sample problem • Gene A and B recombine 5% of the time • Gene B and C recombine 7% of the time • Genes A and C recombine 2% of the time

  8. How to tell genes are NOT linked • When not linked, the F2 generation should show new phenotypes 6/16 of the time. • We will say that genes are not linked if these new phenotypes appear over 37% of the time