27. The five RNAs (U1, U2, U4, U5, and U6) identified in the spliceosome are:
(A) small nucleolar RNAs (snoRNAs).
(B) small nuclear RNAs (snRNAs).
(C) small interfering RNAs (siRNAs).
(D) long non-coding RNAs (lncRNAs).
(E) small rDNA-derived RNAs (srRNAs).

23. Which of the following do NOT typically interact with an elongating RNA polymerase II? (A) Histone-modifying enzymes. (B) Chromatin remodeling complexes. (C) Mediator complexes. (D) Capping enzymes. (E) Histone chaperones.

複選題24. An enhancer: (A) is a trans-acting sequence that stimulates transcription. (B) cannot activate a promoter upstream from this same enhancer. (C) can be located at any distance from a promoter. (D) activates a promoter via an insulator between the enhancer and the promoter. (E) directly interacts with RNA polymerase II to stimulate transcription.

25. Which enzyme is generally linked to transcriptional activation in eukaryotes? (A) Histone methyltransferase. (B) Histone acetyltransferase. (C) Histone phosphorylase. (D) Histone demethylase. (E) Histone deacetylase.

26. Which enzyme is responsible for transcriptional silencing in eukaryotes? (A) DNA methylase. (B) DNA acetylase. (C) DNA polymerase. (D) DNA ligase. (E) DNA endonuclease.

複選題28. Which of the following statements is correct regarding DNA transposition? (A) Autonomous transposons cannot move in the absence of nonautonomous transposons. (B) Virus-like retrotransposition involves target-site-primed reverse transcription. (C) RNA-mediated transposition involves insertion of RNA into a new target site. (D) Transposase cleaves the 5' ends of the element DNA and leaves the 3' terminating strands uncut. These strands are called the nontransferred strands. (E) Replicative transposition results in cointegration with 2 copies of transposon.

29. Which of the following features is true regarding telomerase? (A) It carries its own DNA template. (B) It adds a repeat sequence to the 5' end of telomeres. (C) Its activity is high in somatic cells and low in most cancer cells. (D) It relocates after polymerization reaches the end of the template. (E) It shortens the length of telomeres and leads to disastrous results.

30. During the embryonic development, homeotic genes: (A) determine the dorsal-ventral polarity. (B) control the number of body segments. (C) encode morphogens that establish gradients. (D) are usually expressed by the mother during oogenesis. (E) are defined by mutations that convert one anatomical structure into another.

複選題31. Which of the following components are usually absent in the processed pseudogene that arises from integration of reverse-transcribed mRNAs? (A) Exon. (B) Intron. (C) Poly-A tail. (D) Promoter. (E) 3' untranslated region.

複選題32. Which of the following mutation types may lead to frameshift mutation? (A) Point mutation. (B) Insertion. (C) Deletion. (D) Substitution. (E) Missense mutation.

複選題33. Which of the following features are true regarding tyrosine recombinases? (A) They introduce double-strand breaks. (B) They introduce Holliday junctions. (C) They cleave all four DNA strands before strand exchange. (D) They break and rejoin one pair of DNA strands at a time. (E) They include the Cre recombinase that recognizes the loxP site.