Imagine that you are interested in determining the relative order of three genes
ID: 58601 • Letter: I
Question
Imagine that you are interested in determining the relative order of three genes (x, y, and z) on a bacterial chromosome. You fragment a DNA sample from this species of bacteria and use the resulting fragments to transform a bacterial strain that has non-functional mutant copies of these three genes. By screening the phenotypes of the transformants, you determine the frequency with which each of the following pairs of genes were cotransformed.
Gene Pair Co-Transformation Frequency
x-y 90%
x-z 80%
y-z 65%
What is the order of the three genes on the chromosome? Briefly explain the logic you used to reach this conclusion
Explanation / Answer
Co-transformation of a gene pair is possible when two genes appear closer to each other on the same chromosome.
Since X-Y co transformed 90% they both are more close to each other, the next highest cotransformed gene pair is X-Z. therefore the order of the three genes on the chromosome will be
Y--------X--------Z---
90% 80%