Ch 11

How would the loss of p53 activity affect a cell? All of these choices are correct. DNA damage could accumulate. CDK activity would not be appropriately regulated. The G1 /S checkpoint would not be functional.

All of these choices are correct.

The prokaryotic protein FtsZ is evolutionarily related to eukaryotic tubulin. What does this mean? All of these choices are correct. The amino acid sequence for FtsZ is similar to tubulin. The overall protein structure of FtsZ is similar to tubulin. The two proteins evolved from a common ancestral protein. The gene sequence for FtsZ is similar to tubulin.

All of these choices are correct.

Tumor suppressors oppose oncogenes by: slowing cell division. blocking the action of an oncogene. instructing defective cells to die. repairing mutations. All of these choices are correct.

All of these choices are correct.

What would happen if a pair of sister chromatids only connected to the mitotic spindle at one of their kinetochores? All of these choices are correct. The sister chromatids would not separate. The chromosome would not line up properly at metaphase. One of the daughter cells would have an extra copy of that chromosome.

All of these choices are correct.

Which cellular conditions promote progression of the cell cycle? binding of cyclins to CDKs the expression and synthesis of cyclin proteins the activation of CDKs the accumulation of cyclins All of these choices are correct.

All of these choices are correct.

What is the role of the protein FtsZ in prokaryotes? It is involved in the attachment of DNA to the plasma membrane. It forms a ring at the site of constriction. It is responsible for the replication of DNA. It forms the new cell wall between daughter cells.

It forms a ring at the site of constriction

A researcher is studying phases of the cell cycle in a population of cells during which there is an increase in the DNA content. This stage is most likely: mitosis. cytokinesis. S phase. G1 phase.

S phase.

Which statement is true regarding telomeres? Telomeres are repaired to the same extent in germ cells and somatic cells. Telomeres contain nonessential genes that are not necessary for cell survival. Telomeres are typically only a few base pairs in size. Telomeres are enzymes that repair telomerases, which cap the end of linear chromosomes. Telomeres can contain repeated base sequences.

Telomeres can contain repeated base sequences.

What would happen to the daughter cells if the G2 phase of the parent cell is shortened? The cells would be larger than normal. The cells would not undergo cytokinesis. The cells would be missing chromosomes. The cells would be smaller than normal.

The cells would be smaller than normal.

Which of the answer choices is true regarding CDKs? 1 Loss of CDK activity would lead to cancer. 2 CDKs are active except when they bind to cyclins. 3 The levels of CDKs change with the cell cycle. 4 CDKs are active in cells that enter the G0 phase of the cell cycle.

The levels of CDKs change with the cell cycle.

When a nucleotide is added to a growing nucleic acid strand during DNA replication, the incoming monomer is _____, and the energy required to drive the polymerization is derived from _____. a nucleoside triphosphate; DNA polymerase a nucleoside triphosphate; cleaving a pyrophosphate a nucleoside monophosphate; cleaving ATP DNA; RNA an RNA primer; cleaving a pyrophosphate

a nucleoside triphosphate; cleaving a pyrophosphate

A gene associated with promoting normal cell division is called: a proto-oncogene. a proto-oncogene or a tumor suppressor. an oncogene. a tumor suppressor.

a proto-oncogene

What type of protein is being activated by the G1 / cyclin E-CDK complex to promote the expression of DNA polymerase genes? a synthase a helicase a polymerase a transcription factor

a transcription factor

What characteristics do you expect to observe with a microscope if you investigate the division of mitochondria and chloroplasts in eukaryotic cells? 1 circular DNA attached to the plasma membrane and division by mitosis 2 mitochondria and chloroplasts replicating by a process unlike binary fission or mitosis 3 non-circular DNA and division by mitosis 4 circular DNA attached to the plasma membrane and binary fission

circular DNA attached to the plasma membrane and binary fission

An early observation in the study of the development of sea urchin embryos was that there were several enzymes that became active and then inactive in synchrony with the pattern of rapidly repeating cell divisions. These enzymes had a common characteristic in that they phosphorylate (add phosphate groups to) other proteins. Furthermore, they are only active when bound to another protein—ones that vary in abundance at specific times during the cell cycle. These enzymes are:

cyclin-dependent kinases.

The division of the cell's cytoplasm in a eukaryotic cell is known as: cell fission. mitosis. cytokinesis. both cytokinesis and mitosis.

cytokinesis.

DNA polymerase is the enzyme that separates the two strands of DNA during DNA replication. true false

false

Telomerase activity in stem cells is very low. true false

false

telomerase activity in stem cells is very low. true false

false

Which of the answer choices is part of the process of binary fission in prokaryotes? separation of sister chromatids condensation of chromosomes rearrangement of the microtubule cytoskeleton formation of a new cell wall

formation of a new cell wall

The following enzymes play important roles in DNA replication: DNA polymerase, primase, ligase, helicase. In what order do they work during replication? DNA polymerase, primase, ligase, helicase helicase, primase, DNA polymerase, ligase primase, helicase, ligase, DNA polymerase DNA polymerase, helicase, primase, ligase ligase, helicase, DNA polymerase, primase

helicase, primase, DNA polymerase, ligase

A _____ is an enzyme that adds phosphate groups to other proteins. If this enzyme is only active when bound to a specific protein that fluctuates in concentration in synchrony with the cell cycle, then it is a _____. kinase; cyclin-dependent kinase cyclin; cyclin-dependent kinase cyclin; cyclin-CDK complex kinase; cyclin-CDK complex

kinase; cyclin-CDK complex

The assembly of what cytoskeletal structures is initiated by the cyclin B-CDK complex? All of these choices are correct. microfilament microtubules intermediate filaments

microtubules

The division of genetic material in a eukaryotic cell is called: replication. cytokinesis. binary fission. mitosis.

mitosis.

The point at which DNA synthesis is initiated is called the: primer. start codon. replication fork. primase. origin of replication.

origin of replication.

In which phase of mitosis does the mitotic spindle form? prophase metaphase anaphase telophase

prophase

Reproduction by mitotic cell division: reduces the number of chromosomes by half. results in two daughter cells that are genetically identical. involves the formation of gametes. does not require the replication of chromosomes.

results in two daughter cells that are genetically identical.

In human cells, at the end of mitosis and after cytokinesis, how many chromatids have moved into each daughter cell? 46 23 92 22

46

Why don't plant cells use a contractile ring to divide their daughter cells? Plant cells don't form daughter cells. Plant cells don't have an actin cytoskeleton. A contractile ring can't "pinch" a cell wall. Plant cells don't have plasma membranes.

A contractile ring can't "pinch" a cell wall.

Replication of DNA in a eukaryote occurs during which phase of the cell cycle? S phase M phase G2 phase G1 phase

S phase

Which of the answer options is true regarding DNA replication of a linear chromosome? Both strands get shortened at the same end during replication. Only the lagging strand gets shortened after every other round of replication. Only the leading strand gets shortened during replication. Both strands get shortened at opposite ends during replication. Only the lagging strand gets shortened during replication.

Both strands get shortened at opposite ends during replication.

Select the response that correctly identifies the function of cyclins. Cyclins activate kinases that regulate passage of cell cycle checkpoints. Cyclins replicate DNA during the S phase. Cyclins function as tumor suppressor genes. Cyclins remain in constant concentrations in the cell at all times.

Cyclins activate kinases that regulate passage of cell cycle checkpoints.

Muscle cells in the mammalian heart are multinucleate, meaning that multiple nuclei are present in the cytoplasm of individual large cells. Predict what is different about the cell cycle in a muscle cell. The G1 and G2 phases are extended. Cytokinesis does not occur. S phase happens twice. M phase is inhibited.

Cytokinesis does not occur.

Why are primers needed for DNA replication? They help with the joining of Okazaki fragments. A tiny amount of RNA is needed to tell the cell where genes are located. They help direct the placement of the telomeres. DNA polymerase can only add nucleotides to an existing chain. The primers help with the proofreading function of DNA polymerase.

DNA polymerase can only add nucleotides to an existing chain.

A cell that is not actively dividing is in what phase of the cell cycle? G0 G2 M G1 S

G0

Suppose you are observing some cells with a microscope, and you see a cell that appears to be dividing. You can see that as the cell starts to pinch in half, the DNA seems to be attached to the plasma membrane via a membrane protein. On further analysis, you find that this organism's DNA is circular - that is, it consists of a closed loop. What can you conclude about this organism and its mode of cell division? It is a prokaryote that is dividing by binary fission. It is a eukaryote that is dividing by binary fission. It is a prokaryote that is dividing by mitosis. It is a eukaryote that is dividing by mitosis.

It is a prokaryote that is dividing by binary fission.

Why would a compound that interferes with bacterial cell wall synthesis be useful for treating a bacterial infection? It would prevent replication of DNA, and it would limit the spread of the infection. It would prevent the cells from becoming larger. It would prevent replication of DNA. It would limit growth of the bacterial population through cell division.

It would limit growth of the bacterial population through cell division.

Imagine that a doctor is culturing two types of cells: one from a malignant melanoma and one from a normal skin sample. How would you expect these two cell populations to differ? Malignant melanoma cells would have active telomerases that constantly replenish and lengthen telomeres. Malignant melanoma cells would have telomeres that shorten during successive rounds of replication. Normal skin cells would have telomeres that do not shorten during successive rounds of replication. Malignant melanoma cells would have inactive telomerases, so their telomeres would shorten during successive rounds of replication. Normal skin cells would have active telomerases that constantly replenish and lengthen telomeres.

Malignant melanoma cells would have active telomerases that constantly replenish and lengthen telomeres.

A woman has her genome sequenced and finds that she carries a mutation in p53. Will she develop cancer? Yes, she will certainly develop cancer given the role of p53 in the cell cycle. No, mutations in p53 do not contribute to cancer. Possibly; this mutation is likely to predispose her to developing certain types of cancer.

Possibly; this mutation is likely to predispose her to developing certain types of cancer.

Mitochondria contain their own double-stranded circular DNA and replicate on their own. Why don't they suffer the same consequences as our cells in terms of limited division? 1 because they have high telomerase activity 2 shortening of the DNA is only a problem with nuclear DNA; shortening of mitochondrial DNA is not catastrophic 3 because mitochondrial DNA is circular, it does not shorten when it replicates 4 since mitochondrial DNA only contains a few genes, it can last a lot longer 5 because they have high telomerase activity, and their DNA is circular, so it doesn't shorten in replication

because mitochondrial DNA is circular, it does not shorten when it replicates

Which answer option explains why bacteria can continually divide while they maintain the length of their chromosome? because their DNA is circular, it never shortens after replication because they are so simple because DNA replication is much quicker in bacteria than in eukaryotes because they only have one chromosome because they have plasmids

because their DNA is circular, it never shortens after replication

The process of cell division in a prokaryotic cell is called: binary fission. cytokinesis. mitosis. binary fusion.

binary fission.

Several years ago, a man noticed a small mole on his wrist. Years later, the mole grew in size and the man was diagnosed as having metastatic melanoma. This was likely the result of: 1 several mutations affecting proto-oncogenes and/or tumor suppressor genes. 2 a single mutation inactivating a tumor suppressor gene. 3 a single mutation affecting one proto-oncogene in a cell. 4 None of the other answer options is correct; cancers arise spontaneously, independent of mutations.

several mutations affecting proto-oncogenes and/or tumor suppressor genes.

Many molecular biology lab techniques rely on the fact that even small stretches of complementary nucleic acid sequences have a strong tendency to come together to form the H-bonded base pairing that we recognize as characteristic of the DNA double helix. Which of the answer choices prevents this strong tendency to reassociate from disrupting DNA replication?

single-strand binding protein

Mitotic cell division is considered asexual because: this form of cell division is most similar to binary fission. the daughter cells formed are genetically different. the daughter cells receive DNA from one parent cell, and the daughter cells are genetically identical. the daughter cells get different mixes of maternal and paternal chromosomes.

the daughter cells receive DNA from one parent cell, and the daughter cells are genetically identical.

Energy is required in order to add a nucleotide to the growing strand of DNA during replication. From where does that energy come? helicase DNA ligase the incoming nucleotide primase DNA polymerase

the incoming nucleotide

Which enzyme relieves the tension on the double helix during DNA replication? a single-stranded binding protein helicase DNA polymerase an RNA primer topoisomerase

topoisomerase

DNA polymerase requires both a template and a free 3′ end to elongate a nucleotide chain. true false

true

Evidence exists (especially in dinoflagellates) that mitosis evolved from binary fission. For example, in certain eukaryotic cells during mitosis, DNA is attached to the membrane of the nucleus (much like a circular chromosome of a bacterium is attached to the plasma membrane). true false

true

In circular DNA, the DNA molecule is not shortened during each round of replication. true false

true

Okazaki fragments are ligated to form a continuous DNA molecule after replication is completed. true false

true

Stem cells located in the gastrointestinal tract would possess more active telomerase compared to the amount of telomerase activity in mature neurons of the brain. true false

true

Synthesis of nucleic acids always occurs in the 5′ → 3′ direction. true false

true