A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see? A) inactivation of the selected genes B) decreased chromatin condensationC) abnormalities of mouse embryos D) decreased binding of transcription factorsE) increased chromatin condensation

The correct answer is: B) decreased chromatin condensation

Histone modifications which include phosphorylation, methylation, acetylation and their reverse processes are post-translational modifications that can regulate gene expression. Their effect depends on the amino acid (protein) that is modified, and the combination of the other modifications.

These modifications regulate gene expression by organizing the genome into active form-euchromatin, where DNA is accessible for transcription, or inactive-heterochromatin, where DNA is less accessible for transcription.