Chapter 12, Problem 15P

Drosophila geneticists have isolated many mutations that modify position-effect variegation. Dominant suppressors of variegation [Su(var)s] cause less frequent inactivation of genes brought near heterochromatin by chromosome rearrangements, while dominant enhancers of variegation [E(var)s] cause more frequent inactivation of such genes.

a.	What effects would each of these two kinds of mutations have on position-effect variegation of the white gene in Drosophila (that is, would the eyes be more red or more white)?
b.	Assuming that these Su(var) and E(var) mutations are loss-of-function (null) alleles in the corresponding genes, what kinds of proteins do you think these genes might encode?