57. An unusual example of natural variation in the ploidy occurs in some species. Which of the following statements describes the endopolyploidy most correct?
(A) The endopolyploidy is due to a cell division defect, and it occurs only in lower animals.
(B) Endopolyploidy is the occurrence in somatic tissues； the most common is in human nerve and epidermal cells.
(C) An example of endopolyploidy is in the salivary gland cells of Drosophila, the pairs of chromosomes double approximately 9 times.
(D) The chromosomes undergo repeated rounds of chromosome replication without cellular division, the backup copies of chromosomes kept in vacuoles that segregated away from the functional copies.
(E) The entire organism has extra copies of certain chromosomes, for producing additional gene products.

53.Which of the following statements regarding abscisic acid (ABA) is false? (A) ABA is a plant-specific hormone and does not found in human body. (B) It is a 15-carbon weak acid terpenoid hormone. (C) It is found in high concentrations in newly abscissed leaves. (D) ABA accumulates within seeds during fruit maturation thus preventing premature seed germination. (E) it is synthesized from carotenoids in a series of reactions in plastids and cytoplasm.

54. A pilus (plural: pili) is a hair like structure found on the surface of many bacteria. Which of the following statements regarding pilus is false? (A) It is made of pilin. (B) It participates in the process of bacterial conjugation. (C) Pili are responsible for virulence in many pathogenic strains of bacteria. (D) Pili can protect bacterial cells against bacteriophage. (E) Pili are antigenic.

55. The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following mechanisms likely explains the genetic uniqueness of this population? (A) mutation and natural selection (B) founder effect and genetic drift (C) disassortative mating and divergent selection (D) population bottleneck and Hardy-Weinberg equilibrium (E) heterozygote advantage and stabilizing selection

56. Transcriptome analysis is a tool used in genetic research to determine the mRNAs being produced in a particular tissue, and their relative level of expression. Known genes can therefore be assayed for their expression in different situations. One use of the technology is in cancer diagnosis and treatment. If a known gene functions as a tumor suppressor, predict which of the following pieces of evidence would be most useful in diagnosis of a cancer due to a mutation in this tumor-suppressor gene. (A) The tissue sample shows a high level of gene expression relative to a control (noncancerous) sample. (B) The tissue sample responds to treatment with a mitosis-promoting compound. (C) The tissue sample shows similar expression level of housekeeping genes with a control sample. (D) The mRNAs for cyclins and kinases show unusually high levels of expression. (E) The mRNAs for the targeted tumor suppressor sequence are not expressed.

58.Drosophila is a model animal that is often used in genetic research. Which of the following is the best method for distinguishing the sex of Drosophila?(A) The Y chromosome plays a pivotal role in determining the male sex. Drosophila with Y chromosome is male, the rest is female. (B) Sex combs are located only on the forelegs of male, but not female Drosophila. (C) Male Drosophila is brighter and larger than female. (D) Male Drosophila has red eyes, and female Drosophila has white eyes. (E) Male Drosophila has curled wings, and female Drosophila has flat wings.

59. How do ADH and RAAS work together in maintaining osmoregulatory homeostasis? (A) ADH monitors osmolarity of the blood and RAAS regulates blood volume. (B) ADH monitors appropriate osmolarity by reabsorption of water, and RAAS maintains osmolarity by stimulating Na+ reabsorption. (C)ADH an RAAS work antagonistically； ADH stimulates water reabsorption during dehydration and RAAS removal of water when it is in excess in body fluids. (D) Both stimulate the adrenal gland to secrete aldosterone which increases both blood volume and pressure. (E)Only when they are together in the receptor sites of proximal tubule cells, will reabsorption of essential nutrients back into the blood take place.

60. Which of the following statements about the adrenal gland is correct? (A) During stress, TSH stimulates the adrenal cortex and medulla to secrete acetylcholine. (B) During stress, the alpha cells of islets secrete insulin and simultaneously the beta cells of the islets secrete glucagon. (C) At all times, the adrenal gland monitors calcium levels in the blood and regulates calcium by secreting the two antagonistic hormones, epinephrine and norepinephrine. (D) At all times, the anterior portion secretes ACTH, while the posterior portion secretes oxytocin. (E) During stress, ACTH stimulates the adrenal cortex, and neurons of the sympathetic nervous system stimulate the adrenal medulla.

61. The purpose of the hexose monophosphate shunt is to produce________. (A) pentose phosphates and NADPH (B) DNA and RNA (C) fatty acids (D) reducing substrates (E) ATP

62. Which integral membrane protein is uniquely found in the mitochondria of brown fat? (A) fatty acid synthase (B) catalase (C) ATP Synthase (D) UCP1 (E) FATP

63. What is the mode of action of Vancomycin? (A) Inhibition of cell wall biosynthesis (B) Inhibition of DNA biosynthesis (C) Inhibition of protein biosynthesis (D) Inhibition of folic acid biosynthesis (E) None of the above