68. Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect
(A) the fibers of the mitotic spindle.
(B) anaphase.
(C) formation of the centrioles.
(D) chromatid assembly.
(E) the S phase of the cell cycle.

64. Which of the following is common to both avian and mammalian development? (A) holoblastic cleavage. (B) epiblast and hypoblast. (C) trophoblast. (D) yolk plug. (E) gray crescent.

65. How do the estrous and menstrual cycles compare? (A) Endometrial bleeding occurs during the menstrual cycle; the endometrium is reabsorbed by the uterus during the estrous cycle. (B) There are more pronounced behavioral changes during menstrual cycles than during estrous cycles. (C) There are stronger effects of season and climate on menstrual cycles. (D) Copulation can only occur during the period surrounding ovulation in both the estrous and menstrual cycles. (E) The length of both cycles averages 28 days.

66. A toxin that specifically blocks active transport in the loop of Henle might result in which of the following? (A) A decrease in the interstitial concentration ofNaCl. (B) A decrease in the filtrate concentration ability of the kidney. (C) An increase in the amount of interstitial urea to maintain interstitial osmolarity. (D) A and C only. (E) A, B and C.

67. 'Which of the following is an important distinction between the measurement of basal metabohc rate (BMR) and standard metabolic rate (SMR)? (A) An animal must be fasting for the measurement of SMR. (B) BMRs are performed only on ectothermic animals. (C) An organism must be actively exercising for the measurement ofBMR. (D) SMRs must be determined at a specific temperature. (E) The BMR for a particular animal is usually lower than that animal's SMR.

69. During which phase of aerobic respiration is ATP produced directly by substrate-level phosphorylation? (A) acetyl CoA formation. (B) ethanol production. (C) glucose formation. (D) the Krebs cycle. (E) all of these are true.

70. Short hair (L) is dominant to long hair (l). If a short-haired animal of unknown origin is crossed with a long-haired animal and they produce one long-haired and one short-haired offspring, this would indicate that (A) the short-haired animal was pure-breeding. (B) the short-haired animal was not pure-breeding. (C) the long-haired animal was not pure-breeding. (D) the long-haired animal was pure-breeding. (E) none of these can be determined with two offspring.

71. Conjugation between a bacterium that lacks an F factor (F) and a bacterium that has an F factor on its chromosome (F+) would typically produce which of the following results?(A) The F bacterium ends up carrying one or more plasmids from the F+ bacterium; and the F+ bacterium that lacks those plasmids. (B) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F bacterium, and the F bacterium ends up with an unaltered chromosome. (C) The F+ bacterium ends up with a recombinant chromosome that carries some genes from the F bacterium, and the F-bacterium ends up with a chromosome that lacks those genes. (D) The F bacterium ends up with a recombinant chromosome that carries some genes from the F+ bacterium, and the F+ bacterium ends up with an unaltered chromosome. (E) The Fbacterium ends up with a recombinant chromosome that carries some genes from the F+ bacterium, and the F+ bacterium ends up with a chromosome that lacks those genes.

72. The hypothalamus and pituitary link the activities of the endocrine system and nervous system by (A) neurohormones being secreted in response to the summation of neural messages that enter the hypothalamus. (B) shifts in hormonal concentrations being detected by the anterior pituitary. (C) pheromones being secreted as a response to photoperiodic stimuli. (D) the nervous tissue of the anterior lobe of the pituitary sending stimuli to the glandular tissue of the posterior pituitary to produce hormones that will be secreted by the hypothalamus. (E) all of these are true.

73. ZP3 is a mammalian glycoprotein, which is located in the zona pellucida of eggs where it probably serves two functions: (A) binds to the heads of sperm and prevents the egg from binding an additional sperm. (B) shuts off the function of DNA polymerase and RNA polymerase. (C) directs both the slow and fast block to polyspermy. (D) stimulates the endospenn and initiates RNA synthesis. (E) stimulates protein synthesis and destroys the arcosome.

74. Suppose you know that the genotype of a male lion captured from a wild population is AaBb: You analyze a very large number of gametes from this individual and find all the gametes are of only two types: AB and ab. Vhich of the following is the most reasonable conclusion from this information? (A) The "A" gene and the "B" gene are probably located close together on the same chromosome. (B) There are multiple alleles present at the "B" locus but not at the "A" locus. (C) The parents of this individual were AABB and AABB. (D) Meiosis is not occurring in this individual. (E) Inbreeding is occurring in this individual.