103 Review Questions

3. A diploid cell has_______ the number of chromosomes as a haploid cell.

1. one-fourth
2. half
3. twice
4. four times

4. An organism’s traits are determined by the specific combination of inherited _____.

1. cells.
2. genes.
3. proteins.
4. chromatids.

5. The first level of DNA organization in a eukaryotic cell is maintained by which molecule?

1. cohesin
2. condensin
3. chromatin
4. histone

6. Identical copies of chromatin held together by cohesin at the centromere are called _____.

1. histones.
2. nucleosomes.
3. chromatin.
4. sister chromatids.

7. Chromosomes are duplicated during what stage of the cell cycle?

1. G1 phase
2. S phase
3. prophase
4. prometaphase

8. Which of the following events does not occur during some stages of interphase?

1. DNA duplication
2. organelle duplication
3. increase in cell size
4. separation of sister chromatids

9. The mitotic spindles arise from which cell structure?

1. centromere
2. centrosome
3. kinetochore
4. cleavage furrow

10. Attachment of the mitotic spindle fibers to the kinetochores is a characteristic of which stage of mitosis?

1. prophase
2. prometaphase
3. metaphase
4. anaphase

11. Unpacking of chromosomes and the formation of a new nuclear envelope is a characteristic of which stage of mitosis?

1. prometaphase
2. metaphase
3. anaphase
4. telophase

12. Separation of the sister chromatids is a characteristic of which stage of mitosis?

1. prometaphase
2. metaphase
3. anaphase
4. telophase

13. The chromosomes become visible under a light microscope during which stage of mitosis?

1. prophase
2. prometaphase
3. metaphase
4. anaphase

14. The fusing of Golgi vesicles at the metaphase plate of dividing plant cells forms what structure?

1. cell plate
2. actin ring
3. cleavage furrow
4. mitotic spindle

15. Figure 10.6 Which of the following is the correct order of events in mitosis?

1. Sister chromatids line up at the metaphase plate. The kinetochore becomes attached to the mitotic spindle. The nucleus reforms and the cell divides. Cohesin proteins break down and the sister chromatids separate.
2. The kinetochore becomes attached to the mitotic spindle. Cohesin proteins break down and the sister chromatids separate. Sister chromatids line up at the metaphase plate. The nucleus reforms and the cell divides.
3. The kinetochore becomes attached to the cohesin proteins. Sister chromatids line up at the metaphase plate. The kinetochore breaks down and the sister chromatids separate. The nucleus reforms and the cell divides.
4. The kinetochore becomes attached to the mitotic spindle. Sister chromatids line up at the metaphase plate. Cohesin proteins break down and the sister chromatids separate. The nucleus reforms and the cell divides.

16. At which of the cell-cycle checkpoints do external forces have the greatest influence?

1. G₁ checkpoint
2. G₂ checkpoint
3. M checkpoint
4. G₀ checkpoint

17. What is the main prerequisite for clearance at the G₂ checkpoint?

1. cell has reached a sufficient size
2. an adequate stockpile of nucleotides
3. accurate and complete DNA replication
4. proper attachment of mitotic spindle fibers to kinetochores

18. If the M checkpoint is not cleared, what stage of mitosis will be blocked?

1. prophase
2. prometaphase
3. metaphase
4. anaphase

19. Which protein is a positive regulator that phosphorylates other proteins when activated?

1. p53
2. retinoblastoma protein (Rb)
3. cyclin
4. cyclin-dependent kinase (Cdk)

20. Many of the negative regulator proteins of the cell cycle were discovered in what type of cells?

1. gametes
2. cells in G₀
3. cancer cells
4. stem cells

21. Which negative regulatory molecule can trigger cell suicide (apoptosis) if vital cell cycle events do not occur?

1. p53
2. p21
3. retinoblastoma protein (Rb)
4. cyclin-dependent kinase (Cdk)

22. ___________ are changes to the order of nucleotides in a segment of DNA that codes for a protein.

1. Proto-oncogenes
2. Tumor suppressor genes
3. Gene mutations
4. Negative regulators

23. A gene that codes for a positive cell-cycle regulator is called a(n) _____.

1. kinase inhibitor.
2. tumor suppressor gene.
3. proto-oncogene.
4. oncogene.

24. A mutated gene that codes for an altered version of Cdk that is active in the absence of cyclin is a(n) _____.

1. kinase inhibitor.
2. tumor suppressor gene.
3. proto-oncogene.
4. oncogene.

25. Which molecule is a Cdk inhibitor that is controlled by p53?

1. cyclin
2. anti-kinase
3. Rb
4. p21

26. Which eukaryotic cell-cycle event is missing in binary fission?

1. cell growth
2. DNA duplication
3. karyokinesis
4. cytokinesis

27. FtsZ proteins direct the formation of a _______ that will eventually form the new cell walls of the daughter cells.

1. contractile ring
2. cell plate
3. cytoskeleton
4. septum