35. Which of the following is not true of a codon?
(A) It consists of three nucleotides.
(B) It may code for the amino acid as another codon does.
(C) It never codes for more than one amino acid.
(D) It extends from one end of a tRNA molecule.
(E) It is the basic unit of the genetic code.

31. The extinction of plants has severe consequences because: (A) plants do not have the extensive ranges that animals do. (B) plants require more nutrients than animals. (C) plants require longer periods of time to reproduce than animals. (D) plants are more susceptible to environmental changes than animals. (E) plants are bases of foundations of food webs.

32. A woman had several miscarriages. Her doctor suspected that a hormonal insufficiency was causing the lining of the uterus to break down, as it does during menstruation, terminating her pregnancies. Treatment with which of the following might help her remain pregnant? (A) prolactin (B) oxytocin (C) testosterone (D) luteinizing hormone (E) follicle-stimulating hormone

33. In eukaryotes, what is the active transcription generally associated with? (A) Euchromatin only (B) Heterochromatin only (C) Highly methylated DNA only (D)Very tightly packed DNA only (E) Both euchromatin and highly methylated DNA

34. Which of the following can be used as a cloning vector? (A) E. coli (B) Eco RI (C) lambda phage (D) bacterial plasmid (E) Both C and D are correct

36. The theory that suggests that eukaryotic organelles such as mitochondria and chloroplasts may have originated from a mutualistic relationship between two prokaryotes is referred to as (A) eukaryotic symbiosis. (B) eukaryotic germ theory. (C) eukaryotic coevolution. (D) eukaryotic microevolution. (E) endosymbiotic theory.

37. What percentage of the DNA in a typical eukaryotic cell is expressed at any given time? (A) 3-5% (B) 5-20% (C) 20-40% (D) 40-60% (E) 60-90%

38. What hormone is essential for a tadpole to develop into an adult frog? (A) growth hormone (B) insulin (C) calcitonin (D)glucagons (E) thyroxine

39. Three kinds of selection occur that cause changes in the normal distribution of phenotypes in a population. They are (A) directional selection, disruptive selection, and stabilizing selection. (B) natural selection, artificial selection, and environmental selection. (C) natural selection, genetic drift, and stabilizing selection. (D) microevolution, macroevolution and natural selection. (E) natural selection, artificial selection, and differential selection.

40. In a population that is in Hardy-Weinberg equilibrium, the frequency of the allele a is 0.2. What is the percentage of the population that is heterozygous for this allele? (A) 2 (B) 4 (C) 16 (D) 8 (E) 32

41. Yeast is a member of which division? (A) Ascomycota (B) Zygomycota (C) Basidiomycota (D) Deuteromycota (E) Chytridiomycota