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Chapter 8

Multiple Choice


1. If an intestinal cell in a grasshopper contains 24 chromosomes, a grasshopper sperm cell would contain _ chromosomes.
a.3 b .6 C.12 d.24 e. 48


2. Which of the following phases of mitosis is essentially the opposite of prophase in terms of nuclear changes?
a. telophase b. Metaphase c. S phase d. Interphase e. Anaphase


3. A biochemist measured the amount of DNA in a cell doubled
a. between prophase and anaphase of mitosis
b. between the G1 and G2 phases of the cell cycle
c. during the M phase of the cell cycle
d. between prophase I and prophase II of meiosis
e. between anaphase and telophase of mitosis


4. Which of the following is a function of mitosis in humans?
a. repair of wounds
b. growth
c. multiplication of somatic cells
d. replacement of lost or damaged cells
e. all of the above


5. A micrograph of a dividing cell from a mouse showed 19 chromosomes, each consisting of two sister chromatids. During which of the following stages of cell division could this picture have been taken? (Explain your answer)
a. prophase of mitosis
b. telpphase II of meisosis
c. prophase I of meiosis
d. anaphase of mitosis
e. prophase II of meiosis


6. Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with
a. DNA replication
b. Formation of the mitotic spindle
c. Cleavage
d. Formation of the cell plate
e. Crossing ove 


7. It is difficult to observe indivedual chromsomes during interphase because
a. the DNA has not been replicated yet
b. they have uncoiled to form long, thin strands
c. they leave the nucleus and are dispersed to other parts of the cell
d. homologous chromosomes do not pair up until division starts
e. the spindle must move them to metaphase plate before they become visible.


8. A fruit fly somatic cell contains 8 chromosomes. This means that ——different combinations of chromosomes are possible in its gametes.
a.4 b.8 c.16 d.32 e.64


Thinking as a Scientist


1. Suppose you read in the newspaper that a genetic engineering laboratory has developed a procedure for fusing two gametes from the same person (two eggs two sperm ) to form a zygote. The article mentions that an early step in the procedure prevents crossing over from occurring during the formation of the gametes in the donor's body. The researchers are in the process of determining the genetic makeup of one of their new zygotes. Which of the following predictions do you think they would make? Justify your choice. And explain why you rejected each of the other choices.


a. The zygote would have 46 chromosomes, all of which came from the gamete donor (its one parent), so the zygote would be genetically identical to the gamete donor.
b. The zygote could be genetically identical to the gamete donor, but it is much more likely that it would have an unpredictable mixture of chromosomes from the gamete donor's parents.
c. The zygote would not be genetically identical to the gamete donor, but it would be genetically identical to one of donor's grandparents.


2. Bacteria are able to divide on a much faster schedule than eukaryotic cells. Some bacteria can divide every 20 minutes, while the minimum time required by eukaryotic cells in a rapidly developing embryo is about once per hour, and most cells divide much less often than that. State several testable hypotheses explaining why bacteria can divide at a faster rate than eukaryotic cells.


3. Red blood cells, which carry oxygen to body tissues, live for only about 120 days .Replacement cells are produced by cell division in bone marrow. How many cell divisions must occur each second in your bone marrow just to replace red blood cells? Here is some information to use in calculating your answer. There are about 5 million red blood. (Hints: What is the total number of red blood cells in the body? What fraction of them must be replaced each day if all are replaced in 120 days?)


4. A mule is the offspring of a horse and a donkey. A donkey sperm contains 31 chromosomes and a horse egg 32 chromosomes, to the zygote contains a total 63 chromosomes. The zygote develops normally. The combined set of chromosomes is not a problem in mitosis, and the mulecombined set of the best characteristics of horses and donkeys. However, a mule is sterile; meiosis cannot occur normally in its testes (or ovaries). Explain why mitosis is normal in cells containing both horse and donkey chromosomes, but the mixed set of chromosomes interferes with meiosis.

Chapter 8 Answers


Multiple Choice: 

1.c 2.a 3.b 4.e 5.e (A diploid cell would have an even number of chromosomes; the odd number suggests meiosis I has been completed. Sister chromatids are together only in prophase and metaphase of meiosis II.) 6.c 7.b 8.c