23. Which description is CORRECT for DNA double-strand break?

1. It can induce non-homologous end joining repair

2. It can induce homologous recombination

3. It involves in VDJ recombination, the process that generates diversity on T cell receptors

4. Massive DNA double-strand breaks can lead to cell death

5. It induces H2AX phosphorylation
(A) 1,2,3,4
(B) 2.3,5
(C) 1,2,3
(D) 1,3,4
(E) 1,2,3,4,5,6

19. Which description is CORRECT for exosomes (vesicles)? 1. Membrane-bound extracellular vesicles 2. Contain RNA and proteins 3. Transfer molecules from one cell to another cell 4. Are produced in the endosomal compartment 5. Contain metabolites  6. The diameter is typically below 100 nm (A) 1, 2,3,4 (B) 1,2,3,4,5 (C) 1,2,3,4,5,6 (D) 1,2 (E) 1,2.3

20. Most protein kinases transfer phosphate groups to which amino acid(s)? 1. Glutamate  2. Threonine 3. Serine  4. Tyrosine  5. Lysine  6. Arginine (A) 1,2,3,4 (B) 2,3,5 (C) 1,2,3 (D)2.3.4 (E) 1,2,6

21. Following a nerve impulse, what triggers the opening of plasma membrane voltage-gated Ca2+ channels? (A) Membrane hyperpolarization (B) Endocytosis (C) Membrane depolarization (D) Membrane potential becomes more negative (E) Binding of glucose

22. Which description is INCORRECT for oncogene? (A) A gene that has potential to cause cancer (B) RAS and MYC are oncogenes (C) BRCA1 and p53 are oncogenes (D) The pro-oncogene can become an oncogene by a small modification of its original function. (E) Proto-oncogenes code for proteins that help cell proliferation

24. Which methods can analyze the interaction of DNA and proteins? 1. EMSA (electrophoretic mobility shift assay) 2. Chromatin Immunoprecipitation  3. Yeast two-hybrid system 4. ChIP-seq 5. RNA-seq (A) 1, 2,3,4 (B) 2.3,5 (C) 1,2,3 (D) 1,2,4 (E) 1,2,3,4,5,6

25. Mullis amplified a DNA sequence from genomic DNA by polymerase Chain Reaction (PCR), but he got different sizes of PCR products. Which of the following can improve the specificity? (A) Increase the melting temperate (B) Increase the amount of Taq polymerase (C) Increase the amount of dNTP (D) Increase the concentration of genomic DNA (E) Decrease the temperature of the initial denaturation step

26. George would like to clone X gene into a plasmid. The length of cDNA sequences of X gene, a protein coding gene. is 3000 bp. X protein has ________ amino acids, and its mass is about ________ kDa. Note: Average molecular weight of an amino acid is about 110 daltons. (A)3000, 30 (B) 1000, 110 (C) 1000, 33 (D) 1000, 330 (E) 3000, 330

27. Jennifer ordered the primers for the PCR reaction and received dried oligos in the tubes. She got 30 nanomoles (nmol) oligos of the forward primer, and 25 nanomoles (nmol) oligos of the reverse primer. She would like to the prepare stock solution in 100 nM. How much water should be added into the tubes to make the stock solutions for these primers? (A)300 µl for the forward primer, 250 µl for the reverse primer (B) 30 µl for the forward primer, 25 µl for the reverse primer (C) 3 ml for the forward primer, 2.5 ml for the reverse primer (D)3 µl for the forward primer, 2.5 µl for the reverse primer (E) 30 ml for the forward primer, 25 ml for the reverse primer

28. Which statement of post-translational modification is INCORRECT? (A) Phosphorylation is very common mechanism for regulating the activity of enzymes. (B) Ubiquitylation is usually associated with protein degradation. (C) SUMOylation plays a role in the major DNA repair pathways. (D) O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine or threonine residues in a protein. (E) Acetylation is usually on a glycine residue.

29. Which statement of enhancer is INCORRECT? (A) A region of DNA that can be bound by activators to increase the transcription. (B) It only can be found in eukaryotes. (C) Enhancers can be transcribed into RNAs called enhancer RNAs. (D) The active enhancers are usually in euchromatin. (E) H3K27ac is usually found in an active enhancer.