Exam 2: Mitosis and Meiosis

What is meant by the term chiasma?

List four terms used to describe the normal morphologies,with respect to arm ratio,of eukaryotic chromosomes.

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

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.)

Homologous chromosomes are those that can be matched by virtue of their similar structure and function within a nucleus.Which chromosomes making up a genome do not follow the same characteristics of homology?

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

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 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 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.

Myrmecia pilosula actually consists of several virtually identical,closely related species,with females having chromosome numbers of 18,20,32,48,60,62,and 64.Assume one crossed a female of species (A)with 32 chromosomes and a male of species (B)with 9 chromosomes (males are haploid,and each gamete contains the n complement).How many chromosomes would one expect in the body (somatic)cells of the female offspring?

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?

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

How many haploid sets of chromosomes are present in an individual cell that is tetraploid (4n)?

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?

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?

The house fly,Musca domestica,has a haploid chromosome number of 6.How many chromatids should be present in a diploid,somatic,metaphase cell?

The horse (Equus caballus)has 32 pairs of chromosomes,whereas the donkey (Equus asinus)has 31 pairs of chromosomes.How many chromosomes would be expected in the somatic tissue of a mule?

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

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

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

The centromere of a chromosome separates during anaphase.

Name two cellular organelles,each containing genetic material,which are involved in either photosynthesis or respiration.