Exam 2: Mitosis and Meiosis

The accompanying sketch depicts a cell from an organism in which 2n = 2 and each chromosome is metacentric. a) Circle the correct stage for the cell in this sketch: anaphase of mitosis anaphase of meiosis I anaphase of meiosis II telophase of mitosis b) Given that each G1 nucleus from this organism contains 16 picograms of DNA, how many picograms of chromosomal DNA would you expect in the cell shown below?

You may have heard through various media of an animal alleged to be the hybrid of a rabbit and a cat. Given that the cat (Felis domesticus) has a diploid chromosome number of 38 and a rabbit (Oryctolagus cuniculus) has a diploid chromosome number of 44, what would be the expected chromosome number in the somatic tissues of this alleged hybrid?

Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assume that you are microscopically examining the mitotic and meiotic cells of this organism. You note that in the female, two chromosomal pairs are metacentric and that two pairs are acrocentric. a) Draw the chromosomal configurations as you would expect to see them at the stages listed: Mitotic metaphase First polar body (metaphase) Primary oocyte (metaphase) Ootid (G1) Secondary oocyte (metaphase) b) Given that the above-mentioned cells are from individuals heterozygous for two independently segregating, autosomal loci, plum eyes and curled wings, place appropriate symbols (of your designation) on chromosomes in the drawings you made in part (A) above. Assume no crossing over, and there may be more than one correct answer in some cases. c) Assuming that a somatic G2 nucleus from one of the individuals in this scenario contains about 8.0 picograms of DNA, how much nuclear DNA would you expect in each of the cells mentioned above?

Assume that the somatic cells of a male contain one pair of homologous chromosomes (e.g., AaAb), and an additional chromosome without a homolog (e.g., W). What chromosomal combinations would be expected in the meiotic products (spermatids) of a single primary spermatocyte? (There may be more than one answer.)

If a typical G1 nucleus is 2n and contains 2C (two complements) of DNA, a prophase I cell is 2n and contains 4C of DNA.

The ant, Myrmecia pilosula, is found in Australia and is named bulldog because of its aggressive behavior. It is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words, 2n = 2. (Males are haploid and have just one chromosome.) Which of the following figures would most likely represent a correct configuration of chromosomes in a metaphase I cell of a female?

Living organisms are categorized into two major groups based on the presence or absence of a nucleus. What group is defined by the presence of a nucleus?

The nucleolus organizer (NOR) is responsible for production of what type of cell structure?

Electron microscopy of metaphase chromosomes demonstrated various degrees of coiling. What was the name of the model that depicted this process?

List in order of occurrence the phases of (a) mitosis and (b) prophase I of meiosis.

What is meant by the term chiasma?

Name two evolutionarily significant benefits of meiosis that are not present in mitosis.

Normal diploid somatic (body) cells of the mosquito Culex pipiens contain six chromosomes. Assign the symbols A^mA^p, B^mB^p, and C^mC^p to the three homologous chromosomal pairs. The "m" superscript indicates that the homolog is maternally derived; the "p" indicates a paternally derived homolog. Assume that in the genus Culex, the sex chromosomes are morphologically identical. a) For each of the cell types given below, draw and label (with reference to the symbols defined above) an expected chromosomal configuration. Mitotic metaphase Metaphase of meiosis I Metaphase of meiosis II b) The stage at which "sister chromatids go to opposite poles" immediately follows which of the stages listed in (a)? c) Assuming that all nuclear DNA is restricted to chromosomes and that the amount of nuclear DNA essentially doubles during the S phase of interphase, how much nuclear DNA would be present in each cell listed above? Note: Assume that the G1 nucleus of a mosquito cell contains 3.0 × 10^-12 grams of DNA. d) Given that the sex of Culex is determined by alleles of one gene, males heterozygous, Mm, and females homozygous, mm, illustrate a labeled chromosomal configuration (involving the symbols A^mA^p, B^mB^p, and C^mC^p and the M locus) in a primary spermatocyte at metaphase. Assume that the M locus is on the A^mA^p chromosome and that crossing over has not occurred between the M locus and the centromere.

In an organism with 52 chromosomes, how many bivalents would be expected to form during meiosis?

What is the outcome of synapsis, a significant event in meiosis?

S phase is the part of interphase when DNA duplication takes place.

A chromosome may contain one or two chromatids in different phases of the mitotic or meiotic cell cycle.

What significant genetic function occurs in the S phase of the cell cycle?

What is the name of the membranous structure that compartmentalizes the cytoplasm of eukaryotic organisms?

After which meiotic stage (meiosis I or II) would one expect monads to be formed?