Examples of histone modifications are acetylation (by histone acetyltransferase, or HAT), which is often linked to gene activation, and deacetylation (by histone deacetylases, or HDACs), which often leads to gene silencing typical of heterochromatin. Such heterochromatinizat ion is initiated from a nucleation site and spreads bidirectionally until encountering boundaries that delimit the silenced areas.

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? Select all that apply.

1. The white patches are caused by the acetylation of the histones associated with the DNA of the w + allele.

2. The white patches are caused by the deacetylation of the histones associated with the DNA of the w + allele.

3. The red patches are caused by the acetylation of the histones associated with the DNA of the w + allele.

4. The red patches are caused by the deacetylation of the histones associated with the DNA of the w + allele.