27. Which of the following general statement about a G protein-coupled receptor is true? 　1. It contains twelve transmembrane domains. 　2. It is organized with the N-terminus on the cytoplasmic face of the membrane. 　3. It is organized with the C-terminus on the cytoplasmic face of the membrane. 　4. It is found only in eukaryotes
(A) Only 3 is correct
(B) 2, 4 are correct.
(C) 3, 4 are correct.
(D) 1, 2 are correct.
(E) 1, 3, 4 are correct.

23. Which one is incorrect about transcription factors? (A) Leucine zipper is a dimer formation domain. (B) They can bind to specific DNA elements. (C) They always locate in nuclei. (D) The gene expression is often regulated by transcription activators more than repressors in eukaryotes. (E) They may interact with the Mediator complex.

24. Which one is NOT a component of pre-replication complex? (A) MCM (B) ORC (C) RPA (D) GINS (E) Cdc45

25. Which core histone does NOT have a variant? (A) H2A (B) H2B (C) H3 (D) H4 (E) H1

26. Which of the following classes of noncoding RNAs is directly involved in RNA interference? 1. siRNA2. snoRNA3. piRNA4. miRNA5. hnRNA (A) 1, 3, 4, 5 are involved. (B) 1, 2, 3, 4 are involved. (C) 1, 4, 5 are involved. (D) 1, 3, 4 are involved. (E) All of the above are involved.

28. Which one of the following statements about mitochondrial DNA is incorrect? (A) Products of mitochondrial genes are not exported to cytosol (B) All the mitochondria of a developing embryo are derived from the mother's egg (C) Mitochondrial genetic codes differ from the standard nuclear code (D) Mitochondria contain one non-histone mitochondria DNA molecule (E) Mutations in mitochondrial DNA would cause genetic diseases.

29. Which E3 ligase is involved in sister chromatid segregation during mitosis? (A) APC/C (B) RNF8 (C) RNF168 (D) BRCA1 (E) Cul3-KLHL20

30. Which one is NOT the difference between microtubules and microfilaments? (A) Microfilament is made of G-actin. (B) Microtubule is made of a/ẞ tubulin (C) Dynein is a motor protein in microfilaments. (D) Microtubules have branching. (E) Microtubules need GTP but microfilaments need ATP for their formation.

31. The functional activity of proteins can be modulated by protein modification. Which description is not true? (A) Mass spectrometry is a tool to identify protein modification. (B) Protein phosphorylation occurs at the residues of Ser, Thr, and Tyr. (C) Protein methylation occurs at the residues of Leu and Arg. (D) Histone acetylation results in gene activation. (E) Histone methylation would activate or repress gene expression.

32. Binding of hormone to a receptor tyrosine kinase causes all of the following except: (A) dimerization of the receptor. (B) autophosphorylation of the receptor. (C) activation of Ras through an interaction with GRB2 and Sos. (D) hydrolysis of GTP bound to Ras. (E) All of the above are incorrect.

33. Predict the consequences of a temperature sensitive mutation in which the phosphorylation of the b-catenin protein is blocked. Above the permissive temperature, (A) b-catenin levels will increase and b-catenin will be constitutively active. (B) b-catenin levels will increase and b-catenin will be inactive. (C) b-catenin levels will decrease and cells will be inactive. (D) b-catenin will remain decrease and cells will be more sensitive to Wnt signaling (E) b-catenin will remain constant but cells will be unresponsive to Wnt signaling.