Unformatted text preview: chromosomes! This fact can be used to establish the order of three linked genes. March 19, 2012 BIS101001, Spring 2012--Genes and Gene Expression, R.L. Rodriguez 2012 22 Mapping Tips Mapping studies always start with a test cross Recombination Frequency (RF) increases with the distance between two loci Double crossover events are more rare than single crossovers Only the middle of three loci is changed in a double cross over An odd number of crossovers is need to produce recombinant gametes. Map distances can be additive if double crossovers and interference are accounted for.
March 19, 2012 BIS101001, Spring 2012--Genes and Gene Expression, R.L. Rodriguez 2012 23 Gene Mapping Tips Double crossover progeny are more rare than single crossovers.
q For example, if the probability of one cross over is 0.1 and the probability of another single crossover is 0.15. Using the Product Rule, the probability of both single crossovers (a double crossover) occurring together is the product of the two independent probabilities or, 0.1 x 0.15 = 0.015. Therefore, out of 1000 progeny, there will 100 progen...
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- Genetic linkage, Chromosomal crossover, R.L. Rodriguez ©2012