AP Bio cell cycle, control, and DNA practice MC questions

What is the expected percent change in the DNADNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1G1 phase to the end of the G2G2 phase?

+100%

A group of researchers cultured yeast cells in a nutrient-rich environment and a nutrient-poor environment and observed the duration of the stages of their cell cycles. The results of their study are summarized in Table 1. The cell cycle of yeast cells grown in the nutrient-poor environment is approximately what percent of the cell cycle of yeast cells grown in the nutrient-rich environment?

168

Researchers determined the average amount of time that a particular type of eukaryotic cell spends in each phase of the cell cycle. The data collected by the researchers are represented in Figure 1. Figure 1. The average amount of time spent by a particular type of eukaryotic cell in each phase of the cell cycle Based on Figure 1, what percent of the time required to complete a full cycle do the cells typically spend in interphase?

95%

The diploid number of chromosomes in the cell of a domesticated dog is 7878. Which of the following options includes the correct number of chromosomes in a cell after each cellular process (G2G2 checkpoint, meiosis, and fertilization, respectively)?

After G2G2 Checkpoint 78 After Meiosis 39 After Fertilization 78

Cells that contain only circular chromosomes are most probably which of the following?

Bacterial cells

The diagram above illustrates which of the following processes?

Crossing-over

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. This group of questions refers to the following enzymes. (A) DNA ligase(B) DNA polymerase(C) RNA polymerase(D) Restriction enzyme(E) Reverse transcriptase Enzyme used to position nucleotides during DNA replication

DNA polymerase

Which of the following best describes the role of mitosis in the cell cycle?

Distributing replicated chromosomes to daughter nuclei

Figure 1. The relative concentrations of both the cyclin and CDKCDK components of MPFMPF Maturation promoting factor, MPFMPF, is a cyclin-CDKCDK complex that catalyzes the phosphorylation of other proteins to start mitosis. The activity level of MPFMPF is dependent on the relative concentrations of the cyclin and CDKCDK components of MPFMPF (Figure 1). Based on Figure 1, which of the following describes the role of cyclin in the regulation of the cell cycle?

During MM phase, the cyclin level peaks, resulting in an increased binding frequency with CDKCDK.

Figure 1. Model of crossing over between homologous chromosomes, indicating crossing over rate of selected loci. During prophase II replicated homologous chromosomes pair up and undergo synapsis. What testable question is generated regarding synapsis and genetic variability by Figure 1 ?

Is the distance between two gene loci related to crossover rate?

Scientists have found that DNADNA methylation suppresses crossing-over in the fungus Ascobolus immersus. Which of the following questions is most appropriately raised by this specific observation?

Is the level of genetic variation in the gametes related to the amount of DNADNA methylation observed?

Which of the following is true of mitosis?

It maintains the same chromosome number in the daughter cells as in the parent cell.

All of the following are true statements about meiosis in mammals EXCEPT:

It produces four genetically identical gametes.

Which of the following best describes a characteristic of DNADNA that makes it useful as hereditary material?

Nucleotide bases in one strand can only be paired with specific bases in the other strand.

The sequences for two short fragments of DNA are shown above. Which of the following is one way in which these two segments would differ?

Segment 1 would become denatured at a lower temperature than would segment 2 because A-T base pairs have two hydrogen bonds whereas G-C base pairs have three.

Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing. Which of the following conditions will most likely cause a normal body cell to become a cancer cell?

The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed to induce mitotically dividing S. cerevisiae cells in G2G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes?

The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.

Which of the following best explains why ligase is required for DNADNA replication?

The lagging strand cannot be replicated continuously, and ligase is needed to join the fragments.

When DNA replicates, each strand of the original DNA molecule is used as a template for the synthesis of a second, complementary strand. Which of the following figures most accurately illustrates enzyme-mediated synthesis of new DNA at a replication fork?

arrow on top goes left and outward arrow on the bottom goes right and inward

DNA replication occurs

during the S phase of the cell cycle

A human cell in prophase of mitosis can be distinguished from a human cell in prophase I of meiosis by the presence of

paired homologous chromosomes in the meiotic cell

If 2n = 48 for a particular cell, then the chromosome number in each cell after meiosis would be

24

Cancer can result from a variety of different mutational events. Which of the following is LEAST likely to result in the initiation of a cancerous tumor?

A defect in a cell-cycle checkpoint prevents a cell from entering the S phase.

In most vertebrates, the sperm cell normally contributes which of the following to the new organism?

A haploid complement of chromosomes

Figure 1. Diagram of the cell cycle with key checkpoints Which of the following describes a mutation that would lead to an increase in the frequency of nondisjunction?

A mutation affecting checkpoint 33 proteins that prevents attachment of spindle fibers

Glycogen synthetase kinase 3 beta is a protein kinase that has been implicated in many types of cancer. Depending on the cell type, the gene for glycogen synthetase kinase 3 beta (GSK3β)(GSK3β) can act either as an oncogene or as a tumor suppressor. Which of the following best predicts how GSK3βGSK3β mutations can lead to the development of cancer?

Cells with inactive GSK3βGSK3β fail to trigger apoptosis.

Figure 1 shows the number of chromosomes observed in an actively dividing human cell at each stage of cell division. Figure 1. Number of chromosomes in a human cell at different stages of cell division Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1 ?

Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question. In the 1940's, Avery MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. The transformed cells produced colonies of encapsulated bacteria. Three different procedures and their results are outlined below. Procedure I: Extract made from dead encapsulated cells added to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure II: Extract made from dead encapsulated cells treated with protein-degrading enzymes before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure III: Extract made from dead encapsulated cells treated with DNAse (an enzyme that selectively destroys DNA) before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Only nonencapsulated bacteria grow. A resonable conclusion to draw from the results of the experiment is that

DNA is the genetic material

Figure 1 illustrates a model of the molecules involved in DNADNA replication and their placement relative to each other. Figure 1. Model including molecules involved in DNADNA replication Which of the following correctly explains where DNADNA replication will begin on the strand oriented 5'→3'5′→3′, reading from left to right?

DNADNA replication will be initiated immediately to the left of the RNARNA, since DNADNA polymerase requires an RNARNA primer.

The process depicted in the image above is best summarized by which of the following descriptions?

During meiosis, crossing over leads to recombination of alleles between homologous chromosomes.

Table 1 shows the stage and number of cells and chromosomes per cell at the end of the stage in a 2n=242n=24 organism. Which of the following statements correctly describes the chromosomes in each daughter cell at the end of meiosis II?

Each daughter cell contains 12 chromosomes, each composed of two chromatids. Each chromosome is one of a pair of homologous chromosomes from the parent cell, with the other homologue found in the other daughter cell.

A researcher is conducting an experiment in which cells in different phases of the cell cycle are fused together. The researcher then records what happens to the nuclei of the resulting cell (Table 1). TABLE 1. COMBINATIONS OF CELLS THAT WERE FUSED AND THE PHASE OF NUCLEI IN THE RESULTING CELL Which of the following research questions is best addressed by the experiment?

How do chemical messengers affect a cell's transition between the phases of the cell cycle?

A model showing two possible arrangements of chromosomes during meiosis is shown in Figure 1. Figure 1. Two possible arrangements of chromosomes during meiosis Which of the following questions about genetic diversity could most appropriately be answered by analysis of the model in Figure 1 ?

How does the independent assortment of the two sets of homologous chromosomes increase genetic diversity?

The events listed below generally take place during meiosis. I. Synapsis occurs.II. Crossing-over is completed.III. Condensation of chromosomes begins.IV. Separation of homologous chromosomes begins. Which of the following is the correct sequence of these events?

III, I, II, IV

Researchers performed an experiment to determine the effect of certain genetic mutations on mitosis in tropical fruit fly embryos. They determined the percentage of cells in each of four phases of mitosis as shown in Figure 1. Figure 1. Percent of cells in phases of mitosis Which of the following patterns is shown by the data?

In mutant 3 cells, more time is spent in prophase/prometaphase than in the later stages of mitosis.

Melanocytes are skin cells that can become cancerous and develop into a cancer known as melanoma. Some cancerous melanocytes have developed resistance to the drugs currently used to treat melanoma. As a result, researchers are investigating the effects of a new compound (drug XX) on four different melanoma cell lines. Researchers analyzed cell survival in two cell lines (Figure 1) and oxygen consumption in the presence of drug XX in all four cell lines (Figure 2). Figure 3 shows the proposed mechanism by which drug XX affects cells. Figure 1. Percent survival of normal melanocytes and cancerous melanocyte (melanoma) lines 11 and 22 after treatment with different concentrations of drug XX Figure 2. Oxygen consumption per cell in four melanoma lines after treatment with either solvent alone or solvent containing drug XX. Error bars represent ±2SEx¯±2SEx¯. Figure 3. Pathway leading to cell survival, growth, and proliferation and the likely effect of drug XX Based on Figure 2, which of the following best supports the claim that drug XX inhibits oxygen consumption?

Melanoma line 33 consumes statistically less oxygen per cell in the presence of drug XX than it does in the presence of the solvent alone.

Both mitosis and meiosis begin with a parent cell that is diploid. Which of the following best describes how mitosis and meiosis result in daughter cells with different numbers of chromosomes?

Mitosis produces two identical diploid daughter cells after one round of division. Meiosis produces four haploid daughter cells after two rounds of division.

A model of a process involving nucleic acids is shown in Figure 1. Figure 1. Model of a process involving nucleic acids Which of the following best explains what process is represented in Figure 1 ?

New DNADNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNADNA templates.

Which of the following conclusions is most clearly supported by the representations of nucleic acid #1#1 and nucleic acid #2#2 ?

Nucleic acid #1#1 contains adenine-thymine base pairs, whereas nucleic acid #2#2 does not.

A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell?

Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

During mitosis, which of the following normally occurs?

Replicated chromosomes line up on the equatorial plate.

Which of the following best explains how continuity of genetic information in cells is ensured across generations?

Replication uses a parental strand of DNADNA as a template to create a new strand of DNADNA.

Which of the following occurs in both meiosis and mitosis?

Separation of sister chromatids

Most cells that have become transformed into cancer cells have which of the following characteristics when compared to normal, healthy cells?

Shorter cell cycle

Erwin Chargaff investigated the nucleotide composition of DNADNA. He analyzed DNADNA from various organisms and measured the relative amounts of adenine (AA), guanine (GG), cytosine (CC), and thymine (TT) present in the DNADNA of each organism. Table 1 contains a selected data set of his results. Which of the following statements best explains the data set?

Since the %A%A and the %T%T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNADNA molecule.

The relative amount of DNADNA in a cell at various stages of the cell cycle is shown in Figure 1 . Figure 1. Amount of DNADNA per cell during different stages of the cell cycle, relative to the beginning of the G1G1 stage

The amount of DNADNA is halved as the cell divides into two daughter cells.

Based on the model of eukaryotic cell cycle regulation shown in the figure, which of the following best describes the effect of a drug that blocks the production of the mitotic cyclin?

The cell would be prevented from entering mitosis, and the cell would stop dividing.

A scientist adds a chemical to a culture of dividing cells in order to disrupt DNADNA replication. The replicated DNADNA produced by the cells is double-stranded, but sections of it lack covalent bonds between adjacent nucleotides (Figure 1). Figure 1. Replicated DNADNA produced after a chemical is introduced Which of the following claims is best supported by the data?

The chemical inhibits DNADNA ligase.

Which of the following occurs during mitosis but not during meiosis I ?

The chromatids of each chromosome are separated.

Humans have a diploid number (2n2n) of 4646. Which of the following statements best predicts the consequence if meiosis did not occur during gametogenesis?

The chromosome number would double with each generation.

Figure 1 shows some relevant details of a model of how a deoxynucleotide, in this case dTMPdTMP, is added to a growing strand of DNADNA. Figure 1. Model showing details of adding a deoxythymidine monophosphate (dTMPdTMP) nucleotide to a growing strand of DNA

The phosphate group, attached to the 5′5′ carbon of the dTMPdTMP, forms a covalent bond with the oxygen atom attached to the 3′3′ carbon of the growing strand.

Which of the following best explains why triploid bananas do not produce seeds?

The production of gametes is disrupted because of unequal pairing of homologous chromosomes during meiosis.

Researchers studying cell cycle regulation in budding yeast have observed that a mutation in the CDC15 gene causes cell cycle arrest in telophase when the yeast cells are incubated at an elevated temperature. Which of the following statements best predicts the effect of the cell cycle arrest on proliferating yeast cells?

The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.

Which of the following best describes the cells that result from the process of meiosis in mammals?

They are genetically different from the parent cell.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question. In the 1940's, Avery MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. The transformed cells produced colonies of encapsulated bacteria. Three different procedures and their results are outlined below. Procedure I: Extract made from dead encapsulated cells added to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure II: Extract made from dead encapsulated cells treated with protein-degrading enzymes before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure III: Extract made from dead encapsulated cells treated with DNAse (an enzyme that selectively destroys DNA) before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Only nonencapsulated bacteria grow. What was the purpose of treating the extract with protein-degrading enzymes in Procedure II ?

To demonstrate that the transforming factor is not a protein

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question. In the 1940's, Avery MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. The transformed cells produced colonies of encapsulated bacteria. Three different procedures and their results are outlined below. Procedure I: Extract made from dead encapsulated cells added to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure II: Extract made from dead encapsulated cells treated with protein-degrading enzymes before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Both nonencapsulated and encapsulated bacteria grow. Procedure III: Extract made from dead encapsulated cells treated with DNAse (an enzyme that selectively destroys DNA) before adding extract to culture medium.Nonencapsulated bacteria added to culture medium. Results: Only nonencapsulated bacteria grow. What was the purpose of treating the extract with DNAse in Procedure III ?

To serve as a negative control by demonstrating that transformation does not occur without DNA

Within a forest ecosystem, there is a large amount of diversity among members of a warbler species. Of the following stages of meiosis illustrated for a typical cell, which contributes most to diversity among the warblers?

Touching

Researchers have identified a molecule produced by Ecteinascidia turbinata, a marine invertebrate, from which the drug trabectedin is produced. Soft-tissue tumors treated with trabectedin rapidly decrease in size. In a preliminary study, healthy cells and tumor cells sampled from skin cancer patients treated with trabectedin were collected, and several characteristics of the cells were observed. The observed results of the study are shown in the table. Which of the following best explains the most likely method by which this antitumor drug works?

Trabectedin interferes with the duplication of DNADNA during interphase and thus prevents cancer cells from passing the G2G2 checkpoint.

If chemical signals in the cytoplasm control the progression of a cell to the M phase of the cell cycle, then fusion of a cell in G1 with a cell in early M phase would most likely result in the

condensation of chromatin in preparation of nuclear division in both cells