25. Which one of the following is the best characteristic of microRNAs (miRNAs)?
(A)MicroRNAs are short RNA molecules that encoded by genome.
(B) MicroRNAs can target the genome to suppress gene expression.
(C) MicroRNAs can edit the RNA sequence.
(D)MicroRNAs can edit DNA sequence.
(E)MicroRNAs can edit amino acid sequence of protein.

21. About the phytochrome, which one of the following is the best answer? (A)Pr and Pfr are the same protein. (B) Pr can trigger the flower gene of long-day plant. (C) Pfr can trigger the flower gene of short-day plant. (D)During the night time, the flash of light can increase the level of Pr (E)The night-length can be broken by the flash of light, likewise, the day-length can be broken by covering the black tank.

22. Polysaccharide _____ is an important ECM component for the exoskeleton of many insects and shellfish. (A)collagen (B) laminin (C) proteoglycan (D)chitin (E)glycosaminoglycans

23. The heart is a(n) ________ composed mainly of ________ tissue? (A)tissue, endothelial (B) tissue, connective (C) organ, muscle (D)organ, connective (E)organ, epithelial

24. Which one of the following proteins is involved in synthesizing messenger RNA in eukaryotes? (A)DNA polymerase I (B) DNA polymerase II (C) DNA polymerase III (D)RNA polymerase I (E)RNA polymerase II

26. Bacteria are grown in isotopic 15N (heavy) medium and then transferred to 14N (light) medium and allowed to replicate for 2 generations. The DNA is subsequently isolated and centrifuged in a CsCl2 gradient to yield what type of gradient band(s)? (A)One heavy and one half-heavy band. (B) One light and one half-heavy band. (C) One half-heavy (intermediate to heavy and light) band. (D)One heavy band. (E)One light band.

27. Where would one expect to find the most abundant/active telomerase? (A)Male germ cells that give rise to gametes. (B) A nerve cell from a 2-year-old individual. (C) A nerve cell from a 40-year-old individual. (D)Skin cells from a 2-year-old individual. (E)Skin cells from a 60-year-old individual.

28. ______ is a type of physical mutagens could induce thymine dimer mutations. (A)Gamma rays (B) X-rays (C) Microwave (D)Ultraviolet light (E)Ionizing radiation

29. Which one of the following is the cancer of epithelial cells? (A)Sarcoma. (B) Myeloma. (C) Leukemia. (D)Lymphoma. (E)Carcinoma.

30. When cancer cells can migrate to other parts of the body, they are always said to be____. (A)benign (B) invasive (C) metastatic (D)oncogenic (E)genetic

31. Humans have __________ different types of autosomes. (A)11 (B) 22 (C) 33 (D)44 (E)46