Identify which region of histone molecules are exposed and hence may easily be modified and state the names of the key chemical groups that can be added to histones to affect transcription regulation.

acetyl group, methyl group, or phosphate group

Explanation  Basically different modification can occur to  the tail regions of histone .This includes addition of the groups listed above

The region of the histone molecule that is easily modified is its TAIL.

Explanation:

Histones are a type of alkaline protein that is found on eukaryotic chromatin, packing the former naked DNA into its nucleosome unit. These proteins are both important to 1) compact the incredibly long DNA molecule and, 2) regulating gene expression.

The tail of a histone can suffer the addition of acetyl groups to the molecule (acetylation) or the addition of methyl groups (methylation). These modifications are relevant to the activation or deactivation of genes: acetylation binds the DNA in a much more loosely manner, making it easier for transcription factors to access to it, while methylation does the opposite and provides a tighter bond that deactivates the gene by inhibiting transcription.

it's false. hope i .