BSCI222 Lecture 17 11 5 13 after Test 2 Genetic Mapping Based on recombination rate which correlates with distance in bp between genes but not perfectly o Recombination happens in Meiosis I A lot of the detailed work on recombination was done on common bread mold neurospora because the products of Meiosis spores get held together in a sac called ascus and it s a haploid Diploid from 2 made by fusion immediate Meiosis I then II 4 products then mitotic doubling 8 sets of chromosomes distributed each to a spore o Study diagram of meiosis and mitosis forming the ascus s and s o Which end of the chromosome does the phenotype correspond to The segregation that happened in Meiosis II the pattern of white and black on the and diagram tells you where the segregations happened Different strains have different spore colors looking at the patterns tell you which chromatids exchanged arms At Meiosis I as part of the pairing of the homologues in the synaptonemal complex there is typically at least one chiasma cross over per chromosome arm varies between species and even with size of chromosome but at least one in a typical vertebrate kind of a requirement for progression through meiosis The probability of a chiasma at any interval on a chromosome is roughly proportional to the inverse of the distance really close together less likely to recombine Recombination is essentially random Rest of notes on cheat sheet handout for trihybrid cross
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