Chapter 13, Problem 7P

The two graphs that follow represent genomic sequencing data for two fruit flies with scarlet-colored eyes. Each fly is a heterozygote for a chromosome 3 with normal gene order and a recessive scarlet (st) mutation, and a rearranged chromosome 3; the rearrangements are different in the two flies. Each circle on the graph indicates the number of sequence reads (y coordinate) obtained for a 100 bp sequence starting at the position on chromosome 3 that is shown by the x coordinate.

 

a.	What is the nature of the rearranged chromosome in each fly? What are the approximate locations of the breakpoints defining these rearrangements? How could you find the exact nucleotides at the breakpoints?
b.	Can you conclude that at least part of the st gene lies in a particular region of chromosome 3? If so, give the coordinates of that region defined as precisely as possible.
c.	Is it possible that one or more protein-coding exons of the st gene lie outside of the region you defined in part (b)? Explain.
d.	Does your ability to map the st gene on the basis of these data reflect a recombination experiment or a complementation experiment?