Question

In the heterozygous state (w +/w), a variegated eye is produced, with white and red patches.

How might one explain position-effect variegation in terms of histone acetylation and/or deacetylation?
a. The white patches are caused by the acetylation of the histones associated with the DNA of the w + allele.
b. The white patches are caused by the deacetylation of the histones associated with the DNA of the w + allele.
c. The red patches are caused by the acetylation of the histones associated with the DNA of the w + allele.
d. The red patches are caused by the deacetylation of the histones associated with the DNA of the w + allele.

Answer 1

Answer c), The red patches are caused by the acetylation of the histones associated with the DNA of the w + allele, would be correct.

Step-by-step explanation:

Position-effect variegation can occur when the arrangement of chromosomal material near certain genes leads to inconsistent gene expression, often because of changes in chromatin structure and histone modifications. In the case of variegated eye color in Drosophila, the patches of color are a result of differential expression of the eye pigment gene due to alterations in the chromatin structure at the site of the gene. When histones associated with the DNA are acetylated, the chromatin structure is more open, allowing genes to be expressed, while deacetylation typically results in chromatin condensation and gene silencing.

Therefore, Acetylated histones around the w + allele makes the chromatin more accessible for transcription, leading to the expression of the wild-type, or red-eye, pigment.

Conversely, the white patches are not the result of acetylation, but rather likely a consequence of deacetylated histones resulting in a condensed chromatin state and the silencing of the w+ allele, preventing the production of red pigment.