Cell Reproduction

Figure 10.14 Human papillomavirus can cause cervical cancer. The virus encodes E6, a protein that binds p53. Based on this fact and what you know about p53, what effect do you think E6 binding has on p53 activity? a. E6 activates p53 b. E6 inactivates p53 c. E6 mutates p53 d. E6 binding marks p53 for degradation

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

a. one-fourth

b. half 

c. twice 

d. four times 

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

a. cells. 

b. genes. 

c. proteins. 

d. chromatid 

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

a. cohesin 

b. condensin

c. chromatin 

d. histone 

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

a. histones. 

b. nucleosomes. 

c. chromatin. 

d. sister chromatids. 

Chromosomes are duplicated during what stage of the cell cycle?

a. G1 phase

b. S phase

c. prophase

d. prometaphase 

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

a. DNA duplication

b. organelle duplication

c. increase in cell size

d. separation of sister chromatids 

The mitotic spindles arise from which cell structure? 

a. centromere 

b. centrosome 

c. kinetochore 

d. cleavage furrow

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

a. prophase 

b. prometaphase 

c. metaphase 

d. anaphase 

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

a. prometaphase 

b. metaphase 

c. anaphase 

d. telophase 

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

a. prometaphase 

b. metaphase 

c. anaphase 

d. telophase 

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

a. prophase 

b. prometaphase 

c. metaphase 

d. anaphase 

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

a.    cell plate

b.    actin ring

c.    cleavage furrow

d.    mitotic spindle

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

a.    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.

b.    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.

c.    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.

d.    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.

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

a.    G₁ checkpoint

b.    G₂ checkpoint

c.    M checkpoint

d.    G₀ checkpoint

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

a.    cell has reached a sufficient size

b.    an adequate stockpile of nucleotides

c.    accurate and complete DNA replication

d.    proper attachment of mitotic spindle fibres to kinetochores

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

a.    prophase

b.    prometaphase

c.    metaphase

d.    anaphase

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

a.    p53

b.    retinoblastoma protein (Rb)

c.    cyclin

d.    cyclin-dependent kinase (Cdk)

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

a.    gametes

b.    cells in G0

c.    cancer cells

d.    stem cells

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

a.    p53

b.    p21

c.    retinoblastoma protein (Rb)

d.    cyclin-dependent kinase (Cdk)

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

a.    Proto-oncogenes

b.    Tumor suppressor genes

c.    Gene mutations

d.    Negative regulators

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

a.    kinase inhibitor.

b.    tumor suppressor gene.

c.    proto-oncogene.

d.    oncogene.

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

a.    kinase inhibitor.

b.    tumor suppressor gene.

c.    proto-oncogene.

d.    oncogene.

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

a.    cyclin

b.    anti-kinase

c.    Rb

d.    p21

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

a.    cell growth

b.    DNA duplication

c.    karyokinesis

d.    cytokinesis

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

a.    contractile ring

b.    cell plate

c.    cytoskeleton

d.    septum

What cell-cycle events will be affected in a cell that produces mutated (non-functional) cohesin protein?

Describe how the duplicated bacterial chromosomes are distributed into new daughter cells without the direction of the mitotic spindle.

Compare and contrast a human somatic cell to a human gamete. 

What is the relationship between a genome,

chromosomes, and genes?

Eukaryotic chromosomes are thousands of times longer than a typical cell. Explain how chromosomes can fit inside a eukaryotic nucleus.

Briefly describe the events that occur in each phase of interphase.

Chemotherapy drugs such as vincristine (derived from Madagascar periwinkle plants) and colchicine (derived from autumn crocus plants) disrupt mitosis by binding to tubulin (the subunit of microtubules) and interfering

with microtubule assembly and disassembly. Exactly what mitotic structure is targeted by these drugs and what effect would that have on cell division?

Describe the similarities and differences between the cytokinesis mechanisms found in animal cells versus those in plant cells.

List some reasons why a cell that has just completed cytokinesis might enter the G0 phase instead of the G1 phase.

Describe the general conditions that must be met at each of the three main cell-cycle checkpoints.

Compare and contrast the roles of the positive cell-cycle regulators negative regulators.

What steps are necessary for Cdk to become fully active? 

Rb is a negative regulator that blocks the cell cycle at the G1 checkpoint until the cell achieves a requisite size. What molecular mechanism does Rb employ to halt the cell cycle? 

Outline the steps that lead to a cell becoming cancerous 

Explain the difference between a proto-oncogene and a tumor-suppressor gene.

List the regulatory mechanisms that might be lost in a

cell producing faulty p53.

p53 can trigger apoptosis if certain cell-cycle events fail. How does this regulatory outcome benefit a multicellular organism? 

Name the common components of eukaryotic cell division and binary fission.