Question

Assume that Group 1 of fruit fly eggs had a region from point A to point B on a chromosome inverted and Group 2 had a region from point A to point C inverted on the same chromosome, where A < B < C. (Note that Group 2 had a larger section of the chromosome inverted.) Suppose that no fly in Group 1, with the smaller inversion, was born alive, while Group 2 files lived and functioned normally.

a) Briefly explain why this might happen.

Answer 1

Ans.Inversion involves the change in nucleotide sequences through breakage of a chromosomal segment and reinsertion of the segment by reversing the orientation. Such inversion can lead to deactivation or activation of some genes. Activation and deactivation can also be caused by the size of the fragment undergoing inversion because they involve different nucleotide sequence rearrangements. Hence, some genes which are vital for development might be suppressed due to disruption in genes in the inversion process in group 1 flies leading to death of group 1 flies. On the other hand, some genes required for vital processes for development might be expressed since the inversion did not disrupt the genes and hence group 2 flies lived and functioned normally.