Exam 2: Mitosis and Meiosis

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? A)A B)B C)C D)D E)E

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: mitotic metaphase first polar body (metaphase) primary oocyte (metaphase) ootid (G1) secondary oocyte (metaphase) (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)?

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

What is the outcome of synapsis,a significant event in meiosis? A)side-by-side alignment of nonhomologous chromosomes B)dyad formation C)monad movement to opposite poles D)side-by-side alignment of homologous chromosomes E)chiasma segregation

Which type of cell structure is the nucleolus organizer (NOR)responsible for producing?

List,in order of appearance,all the cell types expected to be formed during (a)spermatogenesis and (b)oogenesis.

In which stage of the cell cycle is G0 located?

When cells withdraw from the continuous cell cycle and enter a "quiescent" phase,which stage are they said to be in?

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

During meiosis,chromosome number reduction takes place in anaphase II.

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.

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

In a healthy male,how many sperm cells would be expected to form from (a)400 primary spermatocytes? (b)400 secondary spermatocytes? A)(a)800; $\quad$$\quad$ (b)800 B)(a)1600; $\quad$$\quad$ (b)1600 C)(a)1600; $\quad$$\quad$ (b)800 D)(a)400; $\quad$$\quad$ (b)400 E)(a)100; $\quad$$\quad$ (b)800

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

Assume that the somatic cells of a male contain one pair of homologous chromosomes (e.g., A_aA_b) 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.)

Assume that an organism has a diploid chromosome number of 6.Two chromosomal pairs are telocentric,and the other pair is metacentric.Assume that the sex chromosomes are morphologically identical.Draw chromosomes as you would expect them to appear at the following stages: primary oocyte (metaphase) secondary spermatocyte (metaphase) first polar body (metaphase)

In a healthy female,how many secondary oocytes would be expected to form from 100 primary oocytes? How many first polar bodies would be expected from 100 primary oocytes? A)200; $\quad$ 50 B)100; $\quad$ 50 C)200; $\quad$ 300 D)100; $\quad$ 100 E)50; $\quad$ 50

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 here?

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.

An organism with a diploid chromosome number of 46 will produce 2²³ combinations of chromosomes at the end of meiosis.