Chapter 14.1 Practice Quiz

The total length of the cell cycle of cells in a cell culture is 24 hours. M phase is found to be 1 hour, S phase is found to be 9 hours and G2 is found to be 4.5 hours. How long is G1? 9.5 hours 1 hour 4.5 hours 24 hours 9 hours

9.5 hours

Checkpoints halt the progress of the cell cycle when: the chromosomal DNA is damaged. the chromosomes are not properly aligned during the M phase. DNA replication during S phase is not completed properly. the DNA cannot be repaired. All of the choices are correct.

All of the choices are correct.

What protein is required to drive the mammalian cell through all cell cycle stages? Wee1 kinase Cdk4 Cdk1 Cdk2 cyklin D1

Cdk1

Cells are exposed to 3H-thymidine for a short period and the first labeled mitotic chromosomes appear about 4 hours later. Why do researchers conclude that G2 lasts about 4 hours? Enzymes were labeled, and they had to build up for 4 hours before they were detectable. The lengths of the other stages of the cell cycle were known, so they could deduce the length of G2 by subtracting them from the total length of the cell cycle. Cells are labeled in the S phase when DNA is replicated, so four hours passed between the end of the S phase and the beginning of the M phase when mitotic chromosomes are first observed. 3H-thymidine only emits radiation for about 4 hours. Other cells of this type have a G2 phase that lasts about 4 hours.

Cells are labeled in the S phase when DNA is replicated, so four hours passed between the end of the S phase and the beginning of the M phase when mitotic chromosomes are first observed.

_______ are surveillance mechanisms that halt the progress of the cell cycle if any of the various events that make up the cell cycle are not working correctly or are not happening in the correct order. Monitors Checkpoints Checkups Surveillosomes

Checkpoints

Cells that have stopped dividing and are arrested in a stage preceding the initiation of DNA synthesis are said to be in a ______ state. G1 phase S phase G2 phase G0 phase

G0 phase

Which part of the cell cycle is the most variable? G1 phase S phase G2 phase M phase

G1 phase

The period in the cell cycle between the end of DNA replication and the beginning of mitosis is called the _____ phase. G1 S G2 G0

G2

What must happen in order for a cell to move from G0 to G1 phase? It must generate an external signal. It must divide. It must receive a growth-promoting signal. It must divide and receive a growth-promoting signal. It must grow extremely large.

It must receive a growth-promoting signal.

Based on cell activities readily visible in the light microscope, there are two major cell cycle phases, ________ and __________. M phase, cytokinesis interphase, cytokinesis M phase, C phase M phase, interphase C phase, interphase

M phase, interphase

What evidence suggests that a cell spends the majority of its time in interphase? Interphase is more useful. A large percentage of cells in a tissue or cell culture are seen to be in mitosis at any given time. Only a small percentage of cells in a tissue or cell culture are seen to be in mitosis at any given time. A moderate percentage of cells in a tissue or cell culture are seen to be in mitosis at any given time. Mitosis is too intricate a process to last very long.

Only a small percentage of cells in a tissue or cell culture are seen to be in mitosis at any given time.

Why did DNA in S-phase nuclei become fragmented when it compacted after fusion of the S-phase cell with an M phase cell? The cell fusion activated enzymes that fragmented the chromosomes. Replicating DNA is especially sensitive to damage, causing compaction to lead to fragmentation. M phase cytoplasm contains enzymes that degrade DNA. M phase cytoplasm contains enzymes that degrade histones.

Replicating DNA is especially sensitive to damage, causing compaction to lead to fragmentation.

DNA synthesis occurs during which phase of the cell cycle? mitosis S phase G1 G2 cytokinesis

S phase

Which of the following statements is NOT true regarding the wee1 gene? Wee1, which is encoded by the wee1 gene, is a protein kinase. Wee1, which is encoded by the wee1 gene, overrides the effect of CAK. Wee1, which is encoded by the wee1 gene, keeps Cdk in an inactive state. The effects of Wee1, which is encoded by the wee1 gene, are reversed by the action of Cdc25. The normal wee1 gene product causes the cells containing it to be smaller, hence the name "wee."

The normal wee1 gene product causes the cells containing it to be smaller, hence the name "wee."

What property below do stem cells possess that is NOT found in most other cells? They secrete lipids and glycolipids. They exhibit synchronous cell division. They exhibit symmetric cell division. The two daughter cells have different properties or fates. They do not replicate their DNA before cell division.

The two daughter cells have different properties or fates.

When normal cells are subjected to treatments that damage DNA, like ionizing radiation or DNA-altering drugs, what happens? They are severely and permanently damaged. Their progress through the cell cycle stops while the damage is repaired. Their progress through the cell cycle continues and the damage is not repaired. The nucleus is thoroughly destroyed.

Their progress through the cell cycle stops while the damage is repaired.

What is the average length of interphase in mammalian cells? There is not a good average since it depends on the cell type and conditions. It may last up to a day. On average, it lasts about 3 hours. It is 12 hours long. It is exactly 10 hours in all cells.

There is not a good average since it depends on the cell type and conditions.

Which statement about the daughter cells that result from mitosis is TRUE? They differ genetically from one another and from the parent cell. They are different from the parent cell, but are genetically identical to one another. One of the daughter cells is genetically identical to the parent cell, and the other daughter cell is not. They are genetically identical to one another and to the parent cell. Daughter cells are always haploid, and parent cells are always diploid.

They are genetically identical to one another and to the parent cell.

What causes the rapid drop in Cdk activity that leads to the exit from mitosis and the entry into G1 typically exhibited by cells as they finish division? a rise in mitotic cyclin concentration a rise in G1 cyclin concentration a plunge in G1 cyclin concentration a plunge in mitotic cyclin concentration

a plunge in mitotic cyclin concentration

What is the average length of M phase in mammalian cells? about 1 hour about a day about 10 hours about 10 minutes 4 hours and 35 minutes

about 1 hour

Checkpoints in the cell cycle _______________. detect cellular abnormalities may allow cells to become senescent recognize DNA damage all are correct choices can "halt" progression through the cell cycle if abnormalities in replication are detected

all are correct choices

What disease can be defined as resulting from a breakdown in a cell's ability to regulate its own division? diabetes cancer heart disease multiple sclerosis emphysema

cancer

The stages through which a cell passes from one cell division to the next constitute the _________. biocycle cell cycle energy cycle regeneration cycle life cycle

cell cycle

Which cells typically have very short cell cycles on the order of less than 30 minutes? mammalian muscle cells cells in mammalian liver tissue cells in a cleaving frog embryo nerve cells both cells in a cleaving frog embryo and mammalian muscle cells

cells in a cleaving frog embryo

The product of the cdc2 gene is: cyclin. MPF. cyclin-dependent kinase. polyubiquitin. CAK.

cyclin-dependent kinase

The regulatory subunit of maturation-promoting factor ________. is called cyclin because its concentration rises and falls predictably as the cell cycle progresses converts ATP to ADP transfers a phosphate group to certain tyrosine residues of specific protein substrates transfers a phosphate group to certain serine and threonine residues of specific protein substrates converts ADP to ATP

is called cyclin because its concentration rises and falls predictably as the cell cycle progresses

The p21 protein: is a Cdc25 inhibitor. is important in stimulating the growth of tumors. prevents cells from entering the M phase. is produced when p53 causes transcription of the p21 gene and translation of the resultant mRNA. is a peptide of 32kD molecular weight.

is produced when p53 causes transcription of the p21 gene and translation of the resultant mRNA.

Wee1 is a ____________ that regulates Cdk2 activity in yeast cells. cyclin kinase phosphatase none of these choices

kinase

Cyclin concentrations are highest during which periods of the cell cycle? late G1 and early S late G2 and early M late G1 and late G2 late M and late S late S and early G2

late G2 and early M

Studies on amphibian oocytes showed that MPF: was not involved in regulating the cell cycle. was produced at a steady rate during the cell cycle. levels fluctuated depending upon the stage of the cell cycle. triggers replication of chromosomes. inhibited maturation of oocytes.

levels fluctuated depending upon the stage of the cell cycle.

When the cyclin concentration _____, cyclin-dependent kinase is activated, causing the cell to: rises; enter the M phase. is low; enter the M phase. is low; enter the S phase. inhibited; immediately undergo cytokinesis. rises; immediately undergo cytokinesis.

rises; enter the M phase.

What stimulus can induce liver cells to proliferate? surgical removal of part of the liver glycogen buildup in the liver interaction with an appropriate antigen interaction with an appropriate antibody a buildup of bile in the liver

surgical removal of part of the liver

If a cell in the G2 phase is fused with a cell in the M phase,: the G2 nucleus will enter the S phase. the M nucleus will enter the G2 phase. the G2 nucleus will enter the M phase. nothing will happen because the chromosomes have already replicated. the chromosomes will be broken into fragments.

the G2 nucleus will enter the M phase.

What determines whether a cell will remain in G2 or progress into mitosis? the balance between the Cdc25 phosphatase and acid phosphatase activities the balance between the Wee1 kinase and the Cdc25 phosphatase activities the balance between Cdk and histones the balance between DNA and nonhistone acidic proteins

the balance between the Wee1 kinase and the Cdc25 phosphatase activities

What triggers the entry of a cell into mitosis? the addition of inhibitory phosphate groups to Cdk1 by the Cdc25 phosphatase the removal of inhibitory phosphate groups from Cdk1 by the Cdc25 phosphatase the addition of inhibitory phosphate groups to Cdk1 by the Wee1 kinase the removal of inhibitory phosphate groups from Cdk1 by the Wee1 kinase

the removal of inhibitory phosphate groups from Cdk1 by the Cdc25 phosphatase

The purpose of the regulation by Wee1 is to make smaller cells. to induce DNA replication. to ensure that G2-phase is completed. none of these choices.

to ensure that G2-phase is completed.