Adding Acetyl and Methyl Groups to a Histone Regulates Gene

Question

Adding acetyl and methyl groups to a histone regulates gene expression by _________________.  
A) increasing the pH of the cell
B) loosening the DNA wound around the histone
C) modifying the nucleotides of the promoter region of the DNA molecule
D) tightening the DNA wound around the histone
E) enhancing the development of a DNA-RNA hybrid

Accepted Answer

The addition of acetyl and methyl groups to a histone can affect the charges on the histone, causing it to loosen or tighten its grip on the DNA. The addition of acetyl groups, for example, can neutralize the positive charges on the histone, making it less likely to bind tightly to the negatively charged DNA. As a result, the DNA may become more accessible to transcription factors and enzymes involved in gene expression, leading to increased gene expression.