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.

20. Which of the following statements is correct regarding imprinting? (A) Imprinting follows the rules of Mendelian inheritance. (B) Histone acetylation is responsible for imprinting. (C) Maintenance methyltransferase is involved in the imprinting process. (D) Sickle cell disorder is a disorder associated with imprinting. (E) Maintenance of the lysogenic state via cell division is an example of imprinting.

21. The λ repressor encoded by the cI gene can act as a repressor or an activator. How does the λ repressor act as an activator to stimulate transcription of the cI gene? (A) It binds to OR2 and contacts RNA polymerase at PRM to stimulate transcription. (B) It binds to OR3 and contacts RNA polymerase at PR to stimulate transcription. (C) It binds to OL2 and contacts RNA polymerase at PLM to stimulate transcription. (D) It binds to OL3 and contacts RNA polymerase at PL to stimulate transcription. (E) It binds to ORE and contacts RNA polymerase at PRE to stimulate transcription.

22. Which of the following nucleotides is hydrolyzed in both transcription and in translation elongation? (A) ATP. (B) CTP. (C) GTP. (D) TTP. (E) UTP.

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.

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.

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).

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.