Question 1

The yeast Saccharomyces cerevisiae reproduces _______________,allowing easy determination of the cell-cycle stage in which a cell is found.

Accepted Answer

Saccharomyces cerevisiae reproduces by budding, which is a form of asexual reproduction. This allows for easy determination of the cell-cycle stage because the size and position of the bud can indicate which stage of the cell cycle the cell is in.

Question 2

The yeast Saccharomyces cerevisiae is particularly useful for genetic analysis of cell-cycle control because

Accepted Answer

Reproduction by budding allows easy identification of the cell-cycle stage. This makes it possible to observe and study the cell cycle in individual cells, and to identify mutants affecting specific stages of the cell cycle.

Question 3

The ____________ checkpoint is disrupted by mutations that alter p53 function.

Accepted Answer

The S-to-G2 checkpoint is disrupted by mutations that alter p53 function, as p53 is responsible for monitoring DNA damage in the cell and initiating either DNA repair or apoptosis. If p53 is inactive or mutated, damaged DNA may be allowed to proceed through the cell cycle, increasing the risk of mutations and cancer. Choice B indicates this checkpoint (S-to-G2) being disrupted.

Question 4

The cell-cycle checkpoint that occurs during mitosis causes nuclear division to pause until

Accepted Answer

The checkpoint during mitosis occurs after chromosomes have lined up at the metaphase plate and before the onset of anaphase. At this checkpoint, the cell checks to make sure that all of the chromosomes have properly attached to the spindle fibers that will pull them apart during anaphase. If there are any unattached or improperly attached chromosomes, the checkpoint will cause the cell to pause in mitosis until the issue is resolved. Once all chromosomes are properly attached, the checkpoint will allow the cell to proceed to anaphase and complete nuclear division.

Question 5

Enzymes that covalently link phosphate groups to their substrates are termed

Accepted Answer

Enzymes that covalently link phosphate groups to their substrates are called kinases.

Question 6

CDKs,such as CDC28,require the assistance of ____________ to carry out their enzymatic activity.

Accepted Answer

CDKs, including CDC28, require the assistance of cyclins to carry out their enzymatic activity. The binding of cyclins to CDKs activates the complex, allowing it to phosphorylate target proteins and drive cell cycle progression.

Question 7

In the cell cycle of Saccharomyces cerevisiae,the appearance of a bud on the surface of a cell indicates that the cell

Accepted Answer

The appearance of a bud on the surface of a cell in Saccharomyces cerevisiae indicates that the cell is reaching the end of G1 phase and preparing to enter S phase, not M phase (A). Mutations in genes regulating G1/S transition (such as the cyclin-dependent kinase Cln/CDK) can affect budding, but such mutations are not specified in the question, so choice B is incorrect. The haploid or diploid state of the cell (C) is not necessarily indicated by the appearance of a bud. Mutations in genes regulating G2/M transition (such as the cyclin-dependent kinase Clb/CDK) would not affect budding, which occurs earlier in the cell cycle, so choice D is incorrect. Therefore, the best choice is E.

Question 8

The temperature at which a cell with a temperature-sensitive mutation is unable to survive is considered the ___________ temperature.

Accepted Answer

The temperature at which a cell with a temperature-sensitive mutation is unable to survive is known as the restrictive temperature. This is the temperature at which the mutant protein in the cell loses its function, leading to cell death or impairment of growth. In contrast, the permissive temperature is the temperature at which the mutant protein retains its function, and the cell can grow and function normally. Hence, the best choice for the given question is A) restrictive temperature.

Question 9

Which of the following does not occur during mitosis?

Accepted Answer

Duplication of chromosomal DNA occurs during the S phase of interphase, which takes place before mitosis. Mitosis is the process of separating replicated chromosomes into two identical nuclei. During mitosis, sister chromatids are segregated, chromosomes condense, the nuclear envelope breaks down, and chromosomes attach to the mitotic spindle.

Question 10

Which of the following is not a common consequence of mutations that eliminate cell-cycle checkpoints?

Accepted Answer

Mutations that eliminate cell-cycle checkpoints would lead to an increased frequency of cell division, not a decreased frequency (as stated in choice B). The other options (A, C, D, and E) are all common consequences of such mutations.

Question 11

Molecules that function to stimulate or inhibit cell division are collectively referred to as

Accepted Answer

Molecules that stimulate or inhibit cell division are known as growth factors. Transcription factors are involved in gene expression, polymerases are involved in DNA replication, kinases are enzymes that phosphorylate proteins, and checkpoints are locations in the cell cycle where the cycle can be halted to check for mistakes or damage.

Question 12

Which of the following is not likely to result from the loss of functional p53?

Accepted Answer

The loss of functional p53 typically leads to a decrease in the cell's ability to arrest in response to DNA damage, not an increase. p53 is crucial for initiating cell cycle arrest to allow for DNA repair or to trigger apoptosis if the damage is irreparable.

Question 13

A programmed cell change that results in cell death is referred to as

Accepted Answer

Apoptosis is a programmed cell death that occurs in multicellular organisms as a normal part of development and maintenance of the body. It is a tightly regulated process that eliminates unwanted or damaged cells without causing inflammation or damage to neighboring cells.

Question 14

Damage to DNA that takes place during DNA replication results in arrest of normal cells at the _______________ checkpoint.

Accepted Answer

The G₂-to-M checkpoint ensures that all DNA is replicated and undamaged before the cell enters mitosis. Damage during replication would arrest the cell at this checkpoint.

Question 15

CDKs associate with cyclins at specific stages of the cell cycle.The CDK subunit is responsible for phosphorylating a substrate protein,while the cyclin is responsible for

Accepted Answer

Cyclins do not have any enzymatic activity and are only responsible for determining which specific proteins the CDK subunit will phosphorylate during different stages of the cell cycle.

Question 16

________________ are proteins that form a structural scaffold on the inner surface of the nuclear membrane.

Accepted Answer

Nuclear lamins are a type of intermediate filament protein that forms a structural scaffold on the inner surface of the nuclear membrane. They play an important role in maintaining the shape and stability of the nucleus, and are also involved in regulating gene expression and DNA replication. Mitotic tubules are structures that form during cell division, chromatin fibrils are long, thin strands of DNA that are tightly packed together with proteins, CDKs (cyclin-dependent kinases) are enzymes that regulate the cell cycle, and histones are proteins that help package DNA into a compact structure called chromatin.

Question 17

The solubility of nuclear lamins is regulated by the _____________ of lamin proteins.

Accepted Answer

The solubility of nuclear lamins is regulated by the phosphorylation state of lamin proteins. Phosphorylation of lamins decreases their solubility, leading to their assembly into the nuclear lamina.

Question 18

The retinoblastoma (Rb)protein regulates progression into S phase by regulating ___________ activity.

Accepted Answer

The Rb protein inhibits cell cycle progression by binding to and sequestering the transcription factor E2F, which is necessary for the expression of genes required for DNA synthesis and cell cycle progression. When Rb is hypophosphorylated, it binds to E2F and represses its transcriptional activity. In order to progress through the G1-S checkpoint, Rb becomes phosphorylated by CDK4/6, leading to the release of E2F and allowing the cell to enter S phase. Therefore, the activity of E2F is regulated by Rb.

Question 19

One characteristic of cancer is unregulated cell proliferation.A second characteristic of cancer cells is

Accepted Answer

The ability of cancer cells to migrate to distant tissues, also known as metastasis, is a distinct characteristic of cancer.

Question 20

The cells in a population of yeast cells in which all members of the population have a temperature-sensitive mutation in the same gene involved in cell-cycle progression will appear _________ when shifted to the restrictive temperature.

Accepted Answer

If all members of the population have the same temperature-sensitive mutation in the same gene involved in cell-cycle progression, then they will all be affected in the same way when shifted to the restrictive temperature. This means that they will all be arrested at the same point in the cell cycle, which will result in the cells being uniform in size and shape.

Quiz 15: Gene Regulation in Prokaryotes