12. Which of the following classes of noncoding RNAs is NOT directly involved in RNA interference? (A) miRNA (B) snoRNA (C) piRNA (D) siRNA

8. The acetylation of lysines on the histone tails... (A)loosens chromatin structure by adding positive charges to histones. (B) recruits the heterochromatin protein HP1, resulting in the establishment of heterochromatin. (C) can be performed on methylated lysines only after they are first demethylated. (D) is a covalent modification and is thus irreversible.