AP Biology : 4.6 Cell Cycle - Exam Style questions with Answer- MCQ

AP PhysicsAP Calculus AP ChemistryAP Biology

Question

A model of the typical life cycle of a cell is shown in Figure 1.

The figure presents the typical life cycle of a eukaryotic cell, depicted by a series of arrows that form a circle. Each arrow is labeled with the name of a stage of the life cycle. Starting at the top and going clockwise, the stages of the life cycle are: M, G 1, S, and G 2. After G 2, two arrows show that the life cycle can either continue on to M or branch away from the cycle.

Figure 1. Typical life cycle of a eukaryotic cell

Scientists have estimated that it takes yeast cells approximately 20 hours to complete the entire cycle. Table 1 shows the amount of time in each phase of the life cycle for yeast cells.

Based on Table 1, what percent of the life cycle of yeast cells is spent in DNA replication?

A. 5 percent

B. 10 percent

C. 25 percent

D. 50 percent

▶️Answer/Explanation

Ans: C
The yeast cells spend 5 hours out of a total of 20 hours in $S$ phase, which is $25%$ .

Question

Researchers grew seedlings of corn, Zea mays, in loose and compact sand. The researchers measured the amount of time required for the cells in the growing root tips of the seedlings to double in number. The mean cell doubling times for the two groups of seedlings are shown in Figure 1.

The figure presents a bar graph with the horizontal axis labeled Sand Type. The sand types, Loose and Compact, are indicated. The vertical axis is labeled Mean Cell Doubling Time, in hours, and the numbers 0 through 40, in increments of 5, are indicated. The data represented in the bar graph are as follows. Note all values are approximate. Sand Type, Loose; Mean Cell Doubling Time, 31 hours. Sand Type, Compact; Mean Cell Doubling Time, 25.5 hours.

Figure 1. Mean cell doubling times for the growing root tips of Zea mays seedlings planted in loose or compact sand

Based on the sample means, which of the following conclusions about the cells in the growing root tips of Zea mays seedlings is best supported by the results of the experiment?

A. The cells of the root tips grow to larger sizes when the seedlings are planted in compact sand than when the seedlings are planted in loose sand.

B. The average rate of mitotic cell division is greater for the root tips growing in loose sand than for the root tips growing in compact sand.

C. The average cell cycle time is greater for the root tips growing in compact sand than for the root tips growing in loose sand.

D. More cells are produced per unit of time in the root tips growing in compact sand than in the root tips growing in loose sand.

▶️Answer/Explanation

Ans: D
According to the figure, the mean cell doubling time of Zea mays seedling root tips in compact sand is less than in loose sand. A lower mean cell doubling time indicates an increased rate of mitotic cell division for cells of root tips in compact sand.

Question

The relative amounts of $DNA$ present in the nucleus of a cell at four different stages of the life cycle are shown in Figure 1.

The figure presents a line graph with a horizontal axis labeled Stage. Stages 1, 2, 3, and 4 are indicated. The vertical axis is labeled Amount of D N A per Cell, and the values 1 x and 2 x are indicated. The data represented by the graph are as follows. The line begins at Stage 1, Amount of D N A per cell, 1 x, and moves horizontally to the right. At the beginning of Stage 2, the line moves upward and to the right, reaching Amount of DNA per Cell, 2 x, by the end of Stage 2. The line continues horizontally, at 2 x, through Stage 3 and approximately three quarters of the way through stage 4. The line then moves downward and to the right, ending at Amount of D N A per cell, 1 x, at the end of Stage 4.

Figure 1. Relative amounts of $DNA$

present in the nucleus of a cell

Based on Figure 1, which of the following statements correctly links a stage of the cell cycle with the event occurring at that stage?

A. Stage $I$ represents the $G 2$ phase of the cell cycle.

B. Synthesis of sufficient $DNA$ for two daughter cells occurs in stage $II$ .

C. Stage $III$ includes mitosis.

D. The replication of genetic material occurs in stage $IV$ .

▶️Answer/Explanation

Ans: B
Stage $II$ represents the $S$ (synthesis) phase of interphase. The genetic information ( $DNA$ ) is doubling. If this did not occur, the daughter cells formed as a result of the cell cycle would have too little genetic information (chromosomes). This process is visible on the graph, as the copies of genetic information increase from one to two copies.

Question

Researchers tracked the amount of $DNA$ (measured in picograms) over time beginning with a single cell and continuing through several rounds of cell division. The researchers observed threadlike chromosomes prior to cell division. The threadlike chromosomes disappeared from view shortly after each division. The amount of $DNA$ in picograms per cell over several rounds of cell division is shown in Figure 1.

The figure presents a diagram of the amount of D N A, in picograms, per cell over several rounds of cell division. From left to right, the diagram is as follows. The diagram begins with a single cell with 3 picograms. The cell then contains 6 picograms. The cell with 6 picograms divides to produce two cells with 3 picograms in each. Each of the cells with 3 picograms then contains 6 picograms. Each of the cells with 6 picograms divides to produce two cells, each with 3 picograms, for a total of 4 cells. Each of the cells with 3 picograms then contains 6 picograms. Each of the cells with 6 picograms divides to produce two new cells, each with 3 picograms, for a total of 8 cells.

Figure 1. Amount of $DNA$ in picograms per cell over several rounds of cell division $DNA$ $DNA$ $DNA$ $DNA$ $DNA$

Which of the following statements is consistent with the data in Figure 1?

A. The cells have a haploid chromosome number of 3.

B. The cells have a diploid chromosome number of 6.

C. There is a change from 3 to 6 picograms of $DNA$ because $DNA$ is replicated before each round of cell division.

D. There is a change from 6 to 3 picograms of $DNA$ after each cell division because the chromosomes lengthen following cell division.

▶️Answer/Explanation

Ans: C
The change from 3 to 6 picograms of $DNA$ prior to replication indicates that the $DNA$ has been replicated. The replicated $DNA$ is condensed into chromosomes during cell division or mitosis. This ensures that the complete genome from a parent cell is passed on to two genetically identical daughter cells.

Question

A cell culture commonly used in research was selected to study the effect of a specific virus on the timing of cell cycle phases. Two separate cultures were started, one untreated and one inoculated with the virus. Both cultures were incubated under identical conditions. After a period of time, 200 cells from each culture were observed and classified as shown in Table 1.

Which of the following most accurately describes an observation and an effect of the viral infection indicated by the data in Table 1?

A. Normal cells spend 98 percent of their time cycling in and out of interphase. The virus reduces this to 5 percent of the time.

B. Twenty percent of the virus-infected cells are in interphase. These cells are no longer part of the cell cycle.

C. Forty percent of the virus-infected cells are in interphase. These cells are preparing for replication of genetic material.

D. Seventy-five percent of the virus-infected cells are found in mitosis. The virus stimulates frequent cell division.

▶️Answer/Explanation

Ans: D
One hundred fifty out of 200 is 75 percent. The virus activates cells currently in the \( $G 0$ phase, leading to rapid cell growth and division.

AP Biology : 4.6 Cell Cycle – Exam Style questions with Answer- MCQ

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