18. Genes in chromosomes packed into _______ fiber show the highest transcriptional activity.
(A) 10 nm
(B) 30 nm
(C)supercoiling
(D) metaphase chromosome
(E)naked DNA

14. Albinism is a recessive trait. A man and woman both show normal pigmentation, but both have one parent who has albinism (without melanin pigmentation). What is the probability that their first child will have albinism? (A) 0 (B) 1/2 (C)1/4 (D) 1 (E)1/16

15. Which one of the following statements is NOT true for signal transduction in the cells? (A) The relay molecules in signaling transduction are often proteins. (B) Many of the relay molecules are protein kinases, and they often act on other protein kinases in the pathway. (C)The activity of a protein regulated by phosphorylation depends on the balance in the cell between active kinases and active phosphatases. (D) Cytoplasmic protein kinases phosphorylate serine or glycine. (E)None of the above.

16. Which of the following statements about independent assortment or segregation is correct? (A) The law of independent assortment describes the behavior of two or more genes relative to one another. (B) The law of segregation describes the behavior of two or more genes relative to one another. (C)The law of independent assortment is accounted for by observations of prophase I of meiosis. (D) The law of segregation is accounted for by anaphase of mitosis. (E)None of the above.

17. It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that________. (A) island forms are descended from mainland forms (B) common environments are inhabited by the same organisms (C)island forms and mainland forms have identical gene pools (D) the island forms and mainland forms are converging (E)None of the above.

19. Which factor and mechanism regulates population growth in negative feedback manner typically so that population growth may follow the logistic growth model? (A) earth quakes； density-dependent (B) infectious disease； density-dependent (C)competition for resources； density-independent (D) toxic wastes； density-independent (E)toxic wastes； competition for resources

20. Given a population that contains genetic variation, what is the correct sequence of the following events under the influence of natural selection? 1. Well-adapted individuals leave more offspring than do poorly adapted individuals. 2. A change occurs in the environment. 3. Genetic frequencies within the population change. 4. Poorly adapted individuals have decreased survivorship. (A) 2→4→1→3 (B) 4→2→1→3 (C)4→2→3→1 (D) 2→4→3→1 (E)3→4→2→1

21. In a comparison of birds and mammals, having four limbs is __________.(A) a shared ancestral character (B) a shared derived character (C)a character useful for distinguishing birds from mammals (D) an example of analogy rather than homology (E)None of the above.

22. Which virus is responsible for causing infectious mononucleosis? (A) Epstein-Barr virus (B) Cytomegalovirus (C)Herpes simplex virus (D) Varicella-zoster virus (E)None of the above.

23. Which is NOT the factor contributed to prokaryotes genetic diversity? (A) Rapid reproduction (B) Genetic recombination (C)Mutation (D) Mutualism (E)All of the above.

24. What part of the bacterial cell helps it move? (A) Capsule (B) The flagella (C)Pili (D) Fimbriae (E)Cilia