Solutions For An Introduction to Genetic Analysis Chapter 5 Problem 39P

b) When these colonies are plated onto three different media,

The possible genotypes grown on the minimal media supplemented with threonine are cys⁺ leu⁺ thr⁺ and cys⁺ leu⁺ thr^-

The possible genotypes grown on the minimal media supplemented with leucine are cys⁺ leu⁺ thr⁺ and cys⁺ leu^- thr⁺

The possible genotypes grown on the minimal media without any supplement is cys⁺ leu⁺ thr⁺

c) The actual genotypes of the colonies on medium (1) had cys⁺ leu⁺ thr^- and medium (2) had cys⁺ leu^- thr⁺. The remaining cultures were cys⁺ leu^- thr^-. Since, none of the genotypes grew on minimal medium and no colony was leu⁺ thr⁺. The remaining percentage of genotype occurred in 100% - 56% = 39% of the colonies.

d) Since, cys and leu are co-transduced, 56 percent of the time. In addition, cys and thr are co-transduced only 5 percent of the time.

Hence, this indicates that the gene cys is closer to leu than it is to thr. cys gene is in the middle because no cys⁺ leu⁺ thr⁺ co-transduced are found.

Therefore, the genetic map showing the order of the three genes is as follows,