46. In a cell dividing by meiosis, DNA is replicated__?
(A) between meiosis I and again before meiosis II；
(B) during prophase I；
(C) before meiosis I；
(D) during prophase II.

42. The structure that organizes the protein subunits of the mitotic spindle is the__? (A) centrosome；(B) centromere；(C) microfilaments；(D) kinetochore.

43. How does the space between our fingers arise? (A) Mitosis of the cells is blocked；(B) The cells die by apoptosis；(C) The cells become part of the fingers；(D) Meiosis of the cells is blocked.

44. In order for a cell to become cancerous, oncogenes must be ___, or tumor suppressors are ___. (A) activated； activated；(B) activated； inactivated；(C) inactivated； inactivated；(D) inactivated； activated.

45. Diploid means having__? (A) the somatic cells have all chromosomes except the sex chromosomes；(B) two complete sets of homologous chromosomes；(C) one complete set of chromosomes in each gamete；(D) both the allele and the autosome form of chromosomes.

47. In meiosis, homologous chromosomes align next to one another during__? (A) prophase I；(B) prophase II；(C) metaphase I；(D) metaphase II.

48. If the heterozygous phenotype is intermediate between those of the two different homozygotes, this is called__? (A) incomplete dominance；(B) independent assortment；(C) polygenic；(D) codominance.

49. Linked genes, by definition, are genes that__? (A) have no alleles；(B) have more alleles than usual；(C) are alleles that are found in different daughter cells；(D) are found on the same chromosome.

50. A single chromosome has__? (A) a single gene with multiple alleles；(B) a single gene with a single allele；(C) multiple genes, each with multiple alleles；(D) multiple genes, each with a single allele.

51. The method used to produce the cloned sheep, Dolly, was__? (A) embryonic stem cell transplantation；(B) polymerase chain reaction；(C) short tandem repeats；(D) somatic cell nuclear transfer.

52. Darwin concluded from his observations of nature and readings that__? (A) population growth is unlimited, leading to the large numbers of organisms；(B) individuals compete with one another for limited resources and only the fittest survive；(C) an individual's likelihood of survival and reproduction are mostly due to chance and changes in the environment；(D) individuals compete with one another for limited resources and only the fittest reproduce.