homework 7
7.01 A species of wasp has three pairs of chromosomes (2n = 6). Chromosome 1 is the longest and is acrocentric, chromosome 2 is somewhat shorter and metcentric, and chromosome 3 is the shortest and is telocentric. Draw a cell of this species as it would appear at metaphase of mitosis. Use one line for each chromatid, and indicate the number (1, 2, or 3) of each chromosome.
7.01 A species of wasp has three pairs of chromosomes (2n = 6). Chromosome 1 is the longest and is acrocentric, chromosome 2 is somewhat shorter and metcentric, and chromosome 3 is the shortest and is telocentric. Draw a cell of this species as it would appear at metaphase of mitosis. Use one line for each chromatid, and indicate the number (1, 2, or 3) of each chromosome.
7.02 The cells shown in the diagram are in various stages of mitosis or meiosis. All the cells come the same individual (a mammal).
7.02 The cells shown in the diagram are in various stages of mitosis or meiosis. All the cells come the same individual (a mammal).
(a) What is the diploid number of chromosomes in this animal?
(a) What is the diploid number of chromosomes in this animal?
(b) How did you arrive at your answer to part (a)?
(b) How did you arrive at your answer to part (a)?
(c) Give the names of each stage shown.
(c) Give the names of each stage shown.
7.03 In a particular plant species, 2n = 12. For this organism, How many chromosomes, and how many DNA molecules will be present per cell for each of the following?
7.03 In a particular plant species, 2n = 12. For this organism, How many chromosomes, and how many DNA molecules will be present per cell for each of the following?
(a) Leaf cell in G1
(a) Leaf cell in G1
(b) Leaf cell in G2
(b) Leaf cell in G2
(c) Root meristem cell in metaphase of mitosis.
(c) Root meristem cell in metaphase of mitosis.
(d) Root meristem cell in anaphase of mitosis.
(d) Root meristem cell in anaphase of mitosis.
(e) Root meristem cell in telophase of mitosis (cytokinesis complete)
(e) Root meristem cell in telophase of mitosis (cytokinesis complete)
(f) Microspore mother cell (in anther) in prophase I of meiosis.
(f) Microspore mother cell (in anther) in prophase I of meiosis.
(g) Microspore mother cell in metaphase II of meiosis.
(g) Microspore mother cell in metaphase II of meiosis.
(h) Pollen grain (after meiosis and cytokinesis complete)
(h) Pollen grain (after meiosis and cytokinesis complete)
7.04 The haploid chromosome number in cats is 19. Sex is determined by the XY system as in humans. Answer the following:
7.04 The haploid chromosome number in cats is 19. Sex is determined by the XY system as in humans. Answer the following:
(a) How many chromosomes are present in a zygote?
(a) How many chromosomes are present in a zygote?
(b) How many sex chromosomes are present in a sperm cell?
(b) How many sex chromosomes are present in a sperm cell?
(c) How many autosomes are present in a liver cell?
(c) How many autosomes are present in a liver cell?
(d) How many X chromosomes are present in an egg cell?
(d) How many X chromosomes are present in an egg cell?
(e) How many Y chromosomes are present in an egg cell?
(e) How many Y chromosomes are present in an egg cell?
(f) During meiosis in the female cat, how many bivalents would be present in the primary oocyte?
(f) During meiosis in the female cat, how many bivalents would be present in the primary oocyte?
7.05 A certain species of animal has 18 chromosomes in its diploid cells (2n=18). Describe what the metaphase chromosome arrangement would look like for this species in each of the following stages: mitosis, meiosis I, and meiosis II.
7.05 A certain species of animal has 18 chromosomes in its diploid cells (2n=18). Describe what the metaphase chromosome arrangement would look like for this species in each of the following stages: mitosis, meiosis I, and meiosis II.
7.06 Explain why the number of chromosomes per cell (N level) remains constant through the cell cycle, but and the amount of DNA per cell (C level) does not. Think how these values change or do not change during G1, S, G2, mitosis, and cytokinesis.
7.06 Explain why the number of chromosomes per cell (N level) remains constant through the cell cycle, but and the amount of DNA per cell (C level) does not. Think how these values change or do not change during G1, S, G2, mitosis, and cytokinesis.
7.07 Consider an individual that is heterozygous for albinism, (Aa).
7.07 Consider an individual that is heterozygous for albinism, (Aa).
(a) What gamete genotypes would you expect this individual to produce, and in what proportions?
(a) What gamete genotypes would you expect this individual to produce, and in what proportions?
(b) Diagram how the chromosomes behave during meiosis to explain your answer to a.
(b) Diagram how the chromosomes behave during meiosis to explain your answer to a.
(c) If this individual is heterozygous for a second gene (Bb) whose locus is on a different chromosome, what gamete genotypes would you expect, and in what proportions?
(c) If this individual is heterozygous for a second gene (Bb) whose locus is on a different chromosome, what gamete genotypes would you expect, and in what proportions?
(d) As you did in part b, illustrate the meiotic chromosome behavior to explain your answer to c. Be sure you understand how this accounts for the principle of independent assortment.
(d) As you did in part b, illustrate the meiotic chromosome behavior to explain your answer to c. Be sure you understand how this accounts for the principle of independent assortment.
7.08 A certain individual has the genotype MmTt. These two genes are located on different chromosomes. This individual can produce four possible types of gametes, but each time a single mother cell undergoes meiosis, only two of the four possible types are produced. Explain why a single meiosis can produce two and only two combinations.
7.08 A certain individual has the genotype MmTt. These two genes are located on different chromosomes. This individual can produce four possible types of gametes, but each time a single mother cell undergoes meiosis, only two of the four possible types are produced. Explain why a single meiosis can produce two and only two combinations.
7.09 Many lower organisms, like algae and fungi, have life cycles based on zygotic meiosis rather than gametic meiosis, which is common in higher animals.
7.09 Many lower organisms, like algae and fungi, have life cycles based on zygotic meiosis rather than gametic meiosis, which is common in higher animals.
(a) How is the sexual process of algae and fungi similar to that of animals?
(a) How is the sexual process of algae and fungi similar to that of animals?
(b) How is it different?
(b) How is it different?
7.10 Ferns, like all vascular plants, have life cycles based on sporic meiosis. For each of the plant parts listed, tell whether cells of that part would be haploid or diploid: leaf, root, egg, antheridium, sporangium, archegonium, sperm, spore.
7.10 Ferns, like all vascular plants, have life cycles based on sporic meiosis. For each of the plant parts listed, tell whether cells of that part would be haploid or diploid: leaf, root, egg, antheridium, sporangium, archegonium, sperm, spore.
7.11 Female honey bees are diploid; male bees are haploid. Male bees produce sperm and can successfully mate with females (queens), eggs can also develop without fertilization (parthenogenesis). Fertilized eggs develop into females, while unfertilized eggs develop into males. How do you think the process of sperm production in male bees differs from sperm production in other insects such as Drosophila?
7.11 Female honey bees are diploid; male bees are haploid. Male bees produce sperm and can successfully mate with females (queens), eggs can also develop without fertilization (parthenogenesis). Fertilized eggs develop into females, while unfertilized eggs develop into males. How do you think the process of sperm production in male bees differs from sperm production in other insects such as Drosophila?