12. Meiosis

Which of the following statements is most accurate?

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

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

What is the function of meiosis?

What is the typical result when a diploid cell has completed meiosis?

Cytokinesis is the __________.

Complete the following table to compare mitosis and meiosis.

What proportion of chromosomes in a man's skin cell are maternal chromosomes?

Sperm and eggs in humans always                   . a. each have two copies of every gene; b. each have one copy of every gene; c. each contain either all recessive alleles or all dominant alleles; d. are genetically identical to all other sperm or eggs produced by that person; e. each contain all of the genetic information from their producer

MAKE CONNECTIONS In Figure 33.7, assume that the two medusae shown at step 4 were produced by one polyp colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to select which of the following is true. (A) Both the medusae and the gametes are genetically identical. (B) Neither the medusae nor the gametes are genetically identical. (C) The medusae are not genetically identical but the gametes are genetically identical. (D) The medusae are genetically identical but the gametes differ genetically.

MAKE CONNECTIONS In Figure 33.8, assume that the two medusae shown at step 4 were produced by one polyp colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to evaluate whether the following sentence is true or false; if false, select the answer that provides the correct reason. Although the two medusae are genetically identical, a sperm produced by one will differ genetically from an egg produced by the other. a. False (both the medusae and the gametes are genetically identical) b. False (neither the medusae nor the gametes are genetically identical) c. False (the medusae are not identical but the gametes are) d. True

Triploid (3n) watermelons, which are seedless, are produced by crossing a tetraploid (4n) strain with a diploid (2n) plant. Explain why this mating produces a triploid individual.

A mule is the offspring of a horse and a donkey. A donkey sperm contains 31 chromosomes and a horse egg cell contains 32 chromosomes, so the zygote contains a total of 63 chromosomes. The zygote develops normally. The combined set of chromosomes is not a problem in mitosis, and the mule combines some of the best characteristics of horses and donkeys. However, a mule is sterile; meiosis cannot occur normally in its testes (or ovaries). Explain why mitosis is normal in cells containing both horse and donkey chromosomes but the mixed set of chromosomes interferes with meiosis.