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.

62. If an egg cell contained EDTA~ a chemical that binds calcium and magnesium, what effects would this have on reproduction? (A) The acrosomal reaction would be blocked. (B) The fusion of sperm and egg nuclei would be blocked. (C) The fast block to polyspermy would not occur. (D) The fertilization envelope would not be formed. (E) The zygote would not contain maternal and paternal chromosomes.

63. Which of the following would probably have the greatest effect on convergent extension? (A) Stopping DNA synthesis. (B) Stopping mRNA synthesis. (C) Releasing an enzyme that digests glycoproteins. (D) A and B only. (E) A, B and C.

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.

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.

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.

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.