How does adding a methyl or acetyl group to a histone protein alter gene activity?

a. A methyl group turns genes off. An acetyl group loosens histone’s grip and increases gene activation.

b. A methyl group turns genes on. An acetyl group tightens histone’s grip and decreases gene activation.

c. A methyl group increases the probability of a mutation, whereas an acetyl group decreases the probability.

d. A methyl group decreases the probability of a mutation, whereas an acetyl group increases the probability.