Chapter 13, Problem 14P

Three strains of Drosophila (Bravo, X-ray, and Zorro) are obtained that are homozygous for three variant forms of a particular chromosome. Karyotype analysis indicates that none of the strains is missing any part of any chromosome. When genetic mapping is performed in the Bravo strain, the following map is obtained (distances in map units).

 

Bravo and X-ray flies are now mated to form Bravo/ X-ray F₁ progeny, and Bravo flies are also mated with Zorro flies to form Bravo/Zorro F₁ progeny. In subsequent crosses, the following genetic distances were found to separate the various genes in the hybrids:

 

a.	Make a map showing the relative order of genes a through h in the X-ray and Zorro strains. Do not show distances between genes.
b.	In the original X-ray homozygotes, would the physical distance between genes c and d be greater than, less than, or approximately equal to the physical distance between these same genes in the original Bravo homozygotes?
c.	In the original X-ray homozygotes, would the physical distance between genes d and e be greater than, less than, or approximately equal to the physical distance between these same genes in the original Bravo homozygotes?