Suppose tetrad analysis is performed with baker’s yeast to determine whether a g

Question

Suppose tetrad analysis is performed with baker’s yeast to determine whether a gene controlling growth rate under normal conditions (S - fast, s - slow alleles) is linked either to a gene required for growth on medium with galactose (G - growth, g - no growth) or to a gene needed for growth at cold temperatures (C- grows well, c- grows poorly). The following haploid strains are crossed and allowed to sporulate to obtain the following tetrad results:

Results of analyzing 200 tetrads per mating Haploid strains mated Parental Ditype Nonparental Ditype Tetratype

A) For each mating, are the genes linked on the same chromosome?

B) If yes, calculate the recombination frequency. If no, explain what data demonstrate that the genes are not linked.

Explanation / Answer

A) Since Parental Ditype is not equal to Non parental ditype the genes are linked on the same chromosome.

B) Recombination frequency = (NPD + 1/2 T)/ Total number of tetrads X 100

For SG x sg the recombination frequency = (88+ 1/2x 21)/200 X 100 = 49.25

For Sc X sC the recombination frequency = (5+ 1/2x48)/200 X 100 = 14.5

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