Chapter 2: Animation Questions (Cell Cycle and Mitosis)

If a cell normally has 12 chromosomes, how many chromosomes are present in the G2 phase of the cell cycle? A. 6 B. 12 C. 24 D. more than 12 but fewer than 24 E. None of the above.

B. 12 Correct. Although the number of DNA molecules double between G1 and G2 of the cell cycle, the number of chromosomes remain the same. Chromosomes can be counted by counting the number of centromeres. Each chromosome in G2 consists of two double-stranded DNA molecules (chromatids) joined by a single centromere.

A cell starts out in G2 phase with 12 chromosomes, but after mitosis, each of the daughter cells has only 11 chromosomes in G1 phase. What event provides the most likely explanation for this scenario? A. During anaphase in the original cell, one of the centromeres didn't divide. B. During prometaphase in the original cell, one of the chromosomes failed to attach to a spindle fiber. C. The DNA in the original cell was not properly replicated in S phase. D. This is not unexpected as the chromosome number drops between G2 and G1 phases of the cell cycle. E. The original cell skipped metaphase during mitosis.

B. During prometaphase in the original cell, one of the chromosomes failed to attach to a spindle fiber. If a spindle fiber fails to attach to a chromosome during prometaphase, that chromosome will fail to migrate to the metaphase plate and will often be lost when the nuclear membranes reform during telophase. This is the most likely explanation for the loss of a single chromosome in both of the daughter cells during mitosis.

During which phase of the cell cycle would each cell be undergoing biochemical events required to prepare for cell division, and each chromosome consist of two identical chromatids? A . G1 B. G2 C. G0 D. S E. None of the above.

B. G2 Correct. During the G2 phase, each chromosome consists of two identical chromatids. The cell undergoes several biochemical events during G2 that are required for chromosome condensation, spindle formation, and nuclear membrane disassembly that take place during M-phase.

If a cell normally has 12 chromosomes, how many DNA molecules are present in metaphase of the cell cycle? A. 6 B. 12 C. 24 D. more than 12 but fewer than 24 E. None of the above.

C. 24 Correct. During metaphase each chromosome consists of two identical, double-stranded DNA molecules. Therefore, if a cell normally contains 12 chromosomes, there will be 24 molecules of DNA during metaphase.

If a cell normally has 12 chromosomes, how many chromosomes are present in anaphase of the cell cycle? A. 6 B. 12 C. 24 D. more than 12 but fewer than 24 E. None of the above.

C. 24 During anaphase each chromosome present in metaphase separates into two chromosomes, each with a single double-stranded DNA molecule. Therefore, during anaphase the chromosome number is temporarily doubled until the cells finish the process of cell division. If a cell normally contains 12 chromosomes, it will contain 24 during anaphase.

If a cell starts out in G2 phase with 12 chromosomes, how many chromosomes would you expect in each of the daughter cells if one of the chromosomes failed to separate in anaphase? A. One daughter cell will have 12 chromosomes and the other will have 13. B. One daughter cell will have 11 chromosomes and the other will have 12. C. Each daughter cell will have 11 chromosomes. D. One daughter cell will have 11 chromosomes and the other will have 13. E. Each daughter cell will have 13 chromosomes.

D. One daughter cell will have 11 chromosomes and the other will have 13 If a chromosome failed to separate into two chromatids during anaphase, both chromatids would travel to the same daughter cell during anaphase. This would mean that one daughter cell would have an extra chromosome and the other daughter cell would be missing a chromosome relative to the original cell that entered mitosis.

In which portion of the cell cycle do chromosomes begin to condense and the spindle fibers begin to form from the centrosomes? A. metaphase B. G2 C. S D. prophase E. anaphase

D. prophase Correct. Chromosomes first begin the process of condensation and spindle fibers begin to form during prophase, a subdivision of mitosis. Chromosome condensation continues through prometaphase when the spindle fibers actually attach to the chromosomes and the nuclear membrane breaks down.

If a cell normally has 12 chromosomes, how many DNA molecules are present in the G1 phase of the cell cycle? a. 6 b. 12 c. 24 d. more than 12 but fewer than 24 e. None of the above

b.12 At the G1 phase of the cell cycle, each chromosome consists of a single chromatid and each chromatid consists of a single double-stranded DNA molecule. Therefore, a cell that normally has 12 chromosomes will have 12 DNA molecules in G1.

What are the two major phases of the cell cycle? a. S phase and M phase b. mitosis and cytokinesis c. interphase and M phase d. prophase and telophase e. G1 and G2

c. interphase and M phase The major phases of the cell cycle are interphase and M phase. All of the other phases listed represent subdivisions of either interphase or M phase.

Which phase of the cell cycle best describes a cell that has exited from active cell division and remains indefinitely with each chromosome consisting of a single chromatid? a. G1 b. G2 c. G0 d. S e. None of the above

c.G0 A cell that has exited from the cell cycle is in G0 phase. This phase is similar to G1 in that each chromosome consists of a single chromatid as the chromosomes have not undergone DNA replication. A cell in G0 can remain in this phase of the cell cycle indefinitely. The difference between G1 and G0 is that a cell in G1 is actively preparing to enter S phase.