Analysis of unordered yeast tetrads from the cross of a hapl

Analysis of unordered yeast tetrads from the cross of a haploid strain with genotype + + + with a strain of genotype a b c yielded the following data. The genotypes of four spores from the same tetrad are listed on each horizontal line. a. Which of these genes are linked, and what is the map distance between them? Show your work. b. Draw a map that illustrates the relative locations of these three genes and their respective centromeres.

Solution

Ans 2(a) If PD>>NPD i.e parental ditype which is atetrad containing 4 haploid cell of parental class is much larger than non parental ditype which is a tetrad containing 4 recombinant haploid cells, then only the two gene are linked.i.e gene in tetrad class 1 which belong to parental ditype is greater then gene in tetrad class 2 belong to NPD are linked. The map distance formula for calculation is M.D= 1/2[(T- 2NPD)+4NPD]/total tetrad)*100=23.