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Unformatted text preview: Problem Set 2A Linkage and mapping (A separate problem set will be made for tetrad analysis) 1. In a plant, leaf color and leaf shape are controlled by two linked genes. Leaves of the wild-type plant are red. A recessive mutation in this gene causes white leaves. Wild- type leaves are pointed, and a recessive mutation in this gene causes them to be smooth. The following crosses were performed: Cross 1: pure breeding white, smooth X pure breeding wild type gives F1: all red, pointed Cross 2: red, pointed F1 X pure breeding white, smooth (test cross) gives F2: 40 smooth 36 red, pointed 10 white, pointed 14 red, smooth a) What is the recombination frequency between the genes for color and shape? b) Using Haldanes mapping function 2x = -ln[1-2RF] calculate the map distance x in centiMorgans. Comment on the applicability of the mapping function in this experiment. 2. Gregor Mendels less well known brother Fritz embarked on yet another series of pea breeding experiments. Peas can be either rough or smooth, and either soft or hard. Fritz crosses true-breeding rough soft peas with true-breeding smooth hard peas and nd all the F1 are rough hard peas. Fritz then crosses these F1 peas with smooth soft peas and nds in the F2: 115 rough soft 110 smooth hard 8 rough hard 12 smooth soft Fritz is puzzled by these results and asks your advice....
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- Spring '08