Ch 18/19: Cell- Division Cycle /Apoptosis/ Mitosis

Progression through the cell cycle requires a cyclin to bind to a Cdk because _________. (a) the cyclins are the molecules with the enzymatic activity in the complex. (b) the binding of a cyclin to Cdk is required for Cdk enzymatic activity. (c) cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle. (d) without cyclin binding, a cell-cycle checkpoint will be activated.

(B) the binding of a cyclin to cdk is required for Cdk enzymatic activity

Which of the following statements about the cell cycle is false? (a) Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells. (b) An unfavorable environment can cause cells to arrest in G1. (c) A cell has more DNA during G2 than it did in G1. (d) The cleavage divisions that occur in an early embryo have short G1 and G2 phases.

(a) once a cell decided to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells

Bax and Bak are (a) pro-apoptotic (b) anti-apoptotic

(a) pro-apoptotic

Bcl-2 family proteins undergo a direct battle with each other during apoptosis. Some members of the family are pro-apoptotic and these proteins (a) promote release of apoptotic factors from the mitochondria (b) prevent apoptosis

(a) promote release of apoptotic factors from the mitochondria

P21, the protein activated by p53 in response to DNA damage is a (a) Cyclin inhibitor (b) Cdk inhibitor (c) Proapoptotic protein

(b) Cdk inhibitor

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only? (a) The mitotic spindle could not assemble (b) The cells produced would get smaller and smaller. (c) Cells would get larger and larger

(b) The cells produced would get smaller and smaller

You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6? (a) Cells will enter S phase prematurely. (b) Cells will be unable to complete DNA synthesis. (c) The origin recognition complex (ORC) will be unable to bind to DNA. (d) Cdc6 will be produced inappropriately during M phase.

(b) cells will be unable to complete DNA synthesis

The decline of M cyclin-cdk activity at the end of mitosis is due to (a) degradation of M Cdk (b) degradation of M cyclin

(b) degradation of M cyclin

Concentrations of cyclins (a) remain same during cell cycle (b) fluctuate during cell cycle

(b) fluctuate during cell cycle

You have isolated a strain of mutant yeast cells that divides normally at 30°C but cannot enter M phase at 37°C. You have isolated its mitotic cyclin and mitotic Cdk and find that both proteins are produced and can form a normal M-Cdk complex at both temperatures. Which of the following temperature-sensitive mutations could not be responsible for the behavior of this strain of yeast? (a) inactivation of a protein kinase that acts on the mitotic Cdk kinase (b) inactivation of an enzyme that ubiquitylates M cyclin (c) inactivation of a phosphatase that acts on the mitotic Cdk kinase (d) a decrease in the levels of a transcriptional regulator required for producing sufficient amounts of M cyclin

(b) inactivation of an enzyme that ubiquitylates M cyclin

Others are anti-apoptotic and these proteins (a) promote release of apoptotic factors from the mitochondria (b) prevent apoptosis

(b) prevent apoptosis

Caspases are (a) kinases that phosphorylate and in turn degrade proteins (b) proteases, that degrade proteins (c) stabilizes proteins during apoptosis

(b) proteases, that degrade proteins

Which of the following statements is false? (a) DNA synthesis begins at origins of replication. (b) The loading of the origin recognition complexes (ORCs) is triggered by S-Cdk. (c) The phosphorylation and degradation of Cdc6 help to ensure that DNA is replicated only once in each cell cycle. (d) DNA synthesis can only begin after prereplicative complexes assemble on the ORCs.

(b) the loading of the origin recognition complexes (ORCs) is triggered by S-Cdk

Concentrations of cyclins drop at each phase due to (a) ubiquitylation (b) ubiquitinylation and proteasomal degradation (c) Phosphorylation

(b) ubiquitinylation and proteasomal degradation

You engineer yeast cells that express the M cyclin during S phase by replacing the promoter sequence of the M cyclin gene with that of S cyclin. Keeping in mind that yeast cells have one common Cdk that binds to all cyclins, which of the following outcomes is least likely during this experiment? (a) There will be both M cyclin-Cdk and S cyclin-Cdk complexes in the cell during S phase. (b) Some substrates that are normally phosphorylated in M phase will now be phosphorylated in S phase. (c) G1 cyclins will be expressed during S phase. (d) S-Cdk targets will be phosphorylated during S phase.

(c) G1 cyclins will be expressed during S phase

Which of the following statement is correct? (a) The level of p53 in normal cell is high (b) DNA damage is due to low level of p53 (c) The level of p53 in normal cell is low

(c) The level of p53 in normal cell is low

Apoptosis differs from necrosis in that necrosis ________________. (a) requires the reception of an extracellular signal. (b) causes DNA to fragment. (c) causes cells to swell and burst, whereas apoptotic cells shrink and condense. (d) involves a caspase cascade.

(c) causes cells to swell and burst, whereas apoptotic cells shrink and condense

Which of the following statements about the anaphase-promoting complex (APC) is false? (a) It promotes the degradation of proteins that regulate M phase.(b) It inhibits M-Cdk activity. (c) It is continuously active throughout the cell cycle. (d) M-Cdk stimulates its activity.

(c) continuously active throughout the cell cycle

The concentration of mitotic cyclin (M cyclin) ________________. (a) rises markedly during M phase. (b) is activated by phosphorylation. (c) falls toward the end of M phase as a result of ubiquitylation and degradation. (d) is highest in G1 phase.

(c) falls toward the end of M phase as a result of ubiquitlylation

Which property of p53 enables it to prevent the development of cancer? (a) p53 prevents cells from triggering apoptosis. (b) p53 is a transcription factor that causes production of proteins that stimulate the cell cycle. (c)p53 prevents the replication of cells with damaged DNA.

(c) p53 prevents the replication of cells with damaged DNA.

How does S-Cdk help guarantee that replication occurs only once during each cell cycle? (a) It blocks the rise of Cdc6 concentrations early in G1. (b) It phosphorylates and inactivates DNA helicase. (c) It phosphorylates the Cdc6 protein, marking it for destruction. (d) It promotes the assembly of a prereplicative complex.

(c) phosphorylates the Cdc6 protein, marking it for destruction

Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2? (a) The cell would be unable to enter M phase. (b) The cell would be unable to enter G2. (c) The cell would enter M phase under conditions when normal cells would not. (d) The cell would pass through M phase more slowly than normal cells

(c) the cell would enter M phase under conditions when normal cells would not

In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? (a) at the transition between G1 and S (b) when cells enter G0 (c) during M (d) at the end of G2

(d) at the end of G2

The G1 DNA damage checkpoint (a) causes cells to proceed through S phase more quickly. (b) involves the degradation of p53. (c) is activated by errors caused during DNA replication. (d) involves the inhibition of cyclin-Cdk complexes by p21.

(d) involves the inhibition of cyclin-cdk complexes by p21

Which of the following events does not usually occur during interphase? (a) DNA is replicated (b)The centrosomes are duplicated (c) cells grows in size (d) nuclear envelope breaks down

(d) nuclear envelope breaks down

Cdks are fully activated, only when they are (a) bound to cyclin (b) phosphorylated (c) dephosphorylated (d) bound to cyclin and phosphorylated (e) bound to cyclin and dephosphorylated

(e) bound to cyclin and dephosphorylated

This human cell has 23 chromosomes. This describes

sperm and ovum

Cdks are (a) kinases (b) phosphatases

(a) kinases

Cdks: (a) add phosphate groups to target proteins (b) remove phosphate groups from target proteins (c) add hydroxyl groups to target proteins

(a) add phosphate groups to target proteins

The number of cells in an adult tissue or animal depends on cell proliferation. What else does it depend on? (a) apoptosis (b) necrosis

(a) apoptosis

Programmed cell death occurs ________________. (a) by means of an intracellular suicide program. (b) rarely and selectively only during animal development. (c) only in unhealthy or abnormal cells. (d) only during embryonic development.

(a) by a means of intracellular suicide program

Bax, Bak trigger release of (a). cytochrome c from mitochondria (b) caspases from mitochondria (c) cytochrome c from ER

(a) cytochrome c from mitochondria

Mitogens are _____. (a) extracellular signals that stimulate cell division. (b) transcription factors important for cyclin production. (c) kinases that cause cells to grow in size. (d) produced by mitotic cells to keep nearby neighboring cells from dividing.

(a) extracellular signals that stimulate cell division

Which of the following does not occur during M phase in animal cells? (a) growth of the cell (b) condensation of chromosomes (c) breakdown of nuclear envelope (d) attachment of chromosomes to microtubules

(a) growth of the cell

Cytochrome c activates (a) initiator caspase (b) executioner caspase

(a) initiator caspase

BAX gene activation by p53 is in response to (a) irreparable DNA damage (b) DNA damage (c) increase in cytochrome c

(a) irreparable DNA damage

Levels of Cdk activity change during the cell cycle, in part because ________________. (a) the Cdks phosphorylate each other. (b) the Cdks activate the cyclins. (c) Cdk degradation precedes entry into the next phase of the cell cycle. (d) cyclin levels change during the cycle.

(d) Cyclin levels change during the cycle