practice quiz

41. The diploid number of chromosomes in a certain animal is 8 (2n = 8). How do the four pairs of homologous chromosomes align and separate during meiosis?

e) They align and assort independently to form any of 16 different combinations.

55. Which of the following events occurs only during organogenesis?

e) differentiation of cells into tissues

28. Cytokinesis is the _____.

e) division of one cell into two

30. Crossing over occurs during _____.

e) prophase I

54. One difference between the blastula and gastrula stages of development is that _____.

e) there is an opening from the cavity inside the gastrula to the outside

23. At the end of telophase I of meiosis and the first cytokinesis, there are _____.

e) two haploid cells

56. The human brain develops from _____.

ectoderm

22. Which of the following results in cells that contain half the parental chromosome number?

meiosis

57. In humans, the skeleton and muscles develop from the embryonic _____.

mesoderm

42. In a diploid set of chromosomes, one member of each pair of homologous chromosomes is derived from the father (paternal), and the other comes from the mother (maternal). If 2n = 6, what is the probability of obtaining a gamete in which all the chromosomes are paternal ones?

1/8

37. Regarding the role of cohesin protein in maintaining cohesion between sister chromatids, which of the following statements is false

b) During meiosis II, cohesion holds sister chromatids along their lengths as the second meiotic spindle forms.

35. Which of the following occurs in meiosis, but not mitosis?

b) Homologous chromosomes separate.

26. Which of the following occurs during anaphase II?

b) Sister chromatids separate and migrate toward opposite poles.

33. Which event occurs only during prophase I of the first meiotic division?

b) Synapsis of homologous pairs occurs.

15. Which of the following statements about homologous chromosomes is correct?

b) They have genes for the same traits at the same loci.

43. The major contribution of sex to evolution is that _____.

b) it provides a method to increase genetic variation

25. Synapsis occurs during _____.

b) prophase I

38. Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?

16

13. How many pairs of autosomes do humans have?

22

40. In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing _____ different types of gametes.

2^23

32. An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?

4

34. In a male mammal, every cell that undergoes meiosis gives rise to _____ sperm.

4

12. In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing _____ chromosomes.

5

48. How does a zygote differ from an ovum?

a) A zygote has more chromosomes.

46. The development of a zygote into a blastula is called _____.

a) Cleavage

8. Which, if any, of the following statements is true?

a) Diploid cells can divide by mitosis. b) Diploid cells can divide by meiosis. c) Haploid cells can divide by mitosis. d) Haploid cells cannot divide by meiosis.

53. What is the embryonic origin of the lining of the digestive tube?

a) Endoderm

27. Which of the following occurs during anaphase I?

a) Homologs separate and migrate toward opposite poles.

52. As an animal develops, organs form and the body transforms into a shape typical of the species, in a process called _____.

a) Morphogenesis

51. What is the most likely trigger of egg activation?

a) a rise in Ca2+ concentration

36. Which function makes meiosis lengthier and more complex than mitosis?

a) decreasing the chromosome number to haploid b) introducing genetic variation among the daughter cells c) ensuring that each daughter cell gets a single, complete set of chromosomes d) undergoing two rounds of cytokinesis

10. In sexually reproducing species, the chromosome number remains stable over time because _____ and _____ always alternate.

a) meiosis ... fertilization

9. Which of the following is part of the life cycle called alternation of generations?

a) multicellular haploid stage (gametophyte) b) multicellular diploid stage (sporophyte) c) zygote d) spores

2. What is a locus?

a) the precise location of a gene on a chromosome

47. Which of the following describes the correct sequence of stages during embryogenesis

a) zygote, cleavage, blastula, gastrula

4. A clone is the product of _____.

asexual reproduction and mitosis

11. The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?

c) 44

45. Which of the following statements reflects an advantage that sexual reproduction likely provides over asexual reproduction?

c) Although energetically more costly than asexual reproduction, sexual reproduction leads to different combinations of alleles that could provide adaptability in a changing environment.

7. Fertilization produces _____.

c) a diploid zygote

14. Sister chromatids _____.

c) are identical copies of each other formed during DNA synthesis

21. Spores and gametes are different in that _____.

c) gametes can fuse to form a zygote, but spores can develop into independent organisms without first forming a zygote

17. When we say that an organism is haploid, we mean that _____.

c) its cells have a single set of chromosomes

49. After a sperm penetrates an egg, a fertilization envelope forms. This envelope _____.

c) prevents more than one sperm from entering the egg

44. Which of the following answers is not involved nor an outcome of crossing over?

c) the random alignment of homologous pairs of chromosome at metaphase I

50. Cell divisions called _____ proceed so rapidly in the developing embryo that there is no growth of the cells between divisions.

cleavage

31. Regions of chromosomes where nonsister chromatids cross over are called _____.

d) Chiasmata

59. Evidence suggests that folic acid may help prevent the development of spina bifida, a common disabling birth defect. It is recommended that women increase their folic acid intake during pregnancy, especially in the first three months. Why is the timing of the folic acid intake relevant?

d) The most drastic and rapid changes, including neural tube formation, are occurring in the embryo.

6. A karyotype is _____.

d) a photograph of all of an individual's chromosomes

20. Nearly all life cycles have both haploid and diploid phases. Usually, the transition from haploid to diploid

d) at fertilization, when gametes fuse

24. What is the result when a diploid cell undergoes meiosis?

d) four haploid cells

16. Humans have 46 chromosomes. This number of chromosomes will be found in _____.

d) liver cells

18. Which of the following is a function of mitosis in humans?

d) multiplication of body cells

5. Unless the chromosomes were stained to show band patterns, a karyotype would be least likely to show which of the following?

d) part of a chromosome turned around

39. Which of the following contributes to genetic variation in sexually reproducing species?

d) random fertilization, independent assortment, crossing over

1. How many genes are present in the human genome?

d) tens of thousands

3. Sexual and asexual reproduction are alike in that _____.

d) they can both occur in multicellular organisms

29. What is the function of meiosis?

d) to make cells with a haploid (half that of the parents) number of chromosomes

19. Somatic cells in humans contain _____ set(s) of chromosomes and are therefore termed _____.

d) two ... diploid

58. In mammals, the _____ facilitates implantation in the uterine wall.

trophoblast