Exam 2: Mitosis and Meiosis

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?

The two terms reductional and equational generally refer to which stages of meiosis (I or II)?

An organism with a haploid number of 10 will produce 1024 combinations of chromosomes at the end of meiosis.

Trisomy 21 or Down syndrome occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome 21. Such individuals therefore have 47 chromosomes. Assume that a mating occurs between a female with Down syndrome and a normal 46 -chromosome male. What proportion of the offspring would be expected to have Down syndrome? Justify your answer.

If a typical G1 nucleus contains 2C (two complements) of DNA, a gamete that is haploid (n) contains 1C of DNA.

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.

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). Which chromosomal combinations would be expected in the meiotic products (spermatids) of a single primary spermatocyte? (There may be more than one answer.)

During interphase of the cell cycle, _.

In which stage of the cell cycle is G0 located?

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 two pairs are acrocentric. a() Draw the chromosomal configurations as you would expect to see them at the stages listed: b() Given that the previously 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 for part (a). Assume no crossing over, and there may be more than one correct answer in some cases. c() Assuming that a somatic G2 nucleus from the individuals mentioned above contains about 8.0 picograms of DNA, how much nuclear DNA would you expect in each of the cells mentioned in part (a)?

For the purposes of this question, assume that a G1 somatic cell nucleus in a female Myrmecia pilosula contains 2 picograms of DNA. How much DNA would be expected in a metaphase I cell of a female?

Organized by the centrioles, what structures are important in the movement of chromosomes during cell division?

Normal diploid somatic (body) cells of the mosquito Culex pipiens contain six chromosomes. Assign the symbols AmAp, BmBp, and CmCp 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 in part (a)? 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 AmAp, BmBp, and CmCp and the M locus) in a primary spermatocyte at metaphase. Assume that the M locus is on the AmAp chromosome and that crossing over has not occurred between the M locus and the centromere.

There is about as much nuclear DNA in a primary spermatocyte as in (how many) spermatids?

A bivalent at pachytene contains four chromatids.

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

What is meant by the term chiasma?

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

The centromere of a chromosome separates during anaphase.

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?