Question

a comparison of mitosis and meiosis
study figure 4.14, which compares mitosis and meiosis. recall that mitosis consists of only one set of division phases and produces two diploid daughter cells that are identical. meiosis, however, consists of two sets of divisions and produces four haploid daughter cells that are not identical. meiosis is important for organisms such as humans because it results in genetic variation. this allows for genetic diversity within a population.
learning check

1. what is the difference between a gamete and a zygote?
2. the diploid number of chromosomes for dogs is 78. how many chromosomes are in the gamete cell of a dog? explain your answer.
3. draw a sketch of a cell at anaphase i. what is the key difference between this phase and anaphase of mitosis?
4. if the number of chromosomes were not reduced during meiosis, how many chromosomes would a human gamete have? how many chromosomes would result after fertilization?
5. what phases of meiosis are most like the phases of mitosis? explain your answer.
6. occasionally, errors occur during meiosis that result in an incorrect number of chromosomes in the daughter cells. during which phase(s) of meiosis are these errors likely to occur? explain.

Explanation:

1. A gamete is a haploid sex - cell (sperm or egg) with half the number of chromosomes of a somatic cell. A zygote is a diploid cell formed by the fusion of two gametes.
2. Gametes are haploid. If the diploid number of chromosomes for dogs is 78, the number of chromosomes in a dog's gamete cell is 39 because meiosis halves the chromosome number.
3. In anaphase I of meiosis, homologous chromosomes separate, while in anaphase of mitosis, sister chromatids separate.
4. Humans have 46 diploid chromosomes. If chromosome number was not reduced during meiosis, a human gamete would have 46 chromosomes. After fertilization, the zygote would have 92 chromosomes.
5. The phases of meiosis II are most like the phases of mitosis because in both, sister chromatids separate.
6. Errors can occur during meiosis I (nondisjunction during anaphase I when homologous chromosomes don't separate properly) or meiosis II (nondisjunction during anaphase II when sister chromatids don't separate properly), resulting in an incorrect number of chromosomes in daughter cells.

Answer:

1. A gamete is a haploid sex - cell; a zygote is a diploid cell formed by gamete fusion.
2. 39
3. In anaphase I, homologous chromosomes separate; in mitotic anaphase, sister chromatids separate.
4. 46; 92
5. Meiosis II phases are most like mitosis phases as sister chromatids separate in both.
6. Nondisjunction can occur in anaphase I or anaphase II.