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APC Question: 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? A.) 168 B.) 127 C.) 179 D.) 160

Answer - A.) 168

APC Question: 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) can act either as an oncogene or as a tumor suppressor. Which of the following best predicts how GSK3β mutations can lead to the development of cancer? A.) Cells with inactive GSK3β fail to trigger apoptosis. B.) Cells with inactive GSK3β fail to proceed past the G2/MG2/M checkpoint. C.) Cells with overactive GSK3β are more likely to repair DNA damage. D.) Cells with overactive GSK3β have longer cell cycles.

Answer - A.) Cells with inactive GSK3β fail to trigger apoptosis.

APC Question: Air is less dense at very high elevations, so less oxygen is available than in the denser air at sea level. Based on the model in Figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level? A.) More erythropoietin will be secreted from the kidneys, decreasing production of erythrocytes. B.) More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes. C.) Less erythropoietin will be secreted from the kidneys, decreasing production of erythrocytes. D.) Less erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.

Answer - B.) More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.

APC Question: The coagulation cascade controls blood clot formation in response to blood vessel injury. Thrombin is an enzyme that plays a key role in regulating the coagulation cascade. A simplified model of thrombin's role in regulating the coagulation cascade is represented in Figure 1. Argatroban is a competitive inhibitor of thrombin. Which of the following effects on the coagulation cascade is most likely to result from inhibiting thrombin activity with argatroban? A.) The activation of clotting factors will be blocked. B.) The rate of fibrin formation will decrease. C.) Thrombin will be converted to prothrombin. D.) The rate of blood clot formation will increase.

Answer - B.) The rate of fibrin formation will decrease.

APC Question: Figure 1 shows the number of chromosomes observed in an actively dividing human cell at each stage of cell division. Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1? A.) DNA replication occurs between metaphase and anaphase, doubling the number of chromosomes. Between telophase and cytokinesis, the cell divides in two, with each cell receiving half of the replicated chromosomes. B.) New chromosomes formed during prophase are doubled during anaphase and are recombined before cytokinesis. C.) 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. D.) At anaphase a cell contains two identical copies of each chromosome, but following telophase, one of the copies is broken down into nucleotides.

Answer - C.) 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.

APC Question: 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. Which of the following patterns is shown by the data? A.) Mutant 1 cells are more similar to mutant 3 cells than to wild-type cells. B.)In wild-type cells, the percent of cells in anaphase is twice the amount of those in telophase C.) In mutant 3 cells, more time is spent in prophase/prometaphase than in the later stages of mitosis. D.) The percent of mutant 2 cells in anaphase is higher than that of mutant 1 cells.

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

APC Question: The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. A simplified model of the epinephrine signaling pathway is represented in Figure 1. Cyclic AMP phosphodiesterase is an enzyme that catalyzes the conversion of cyclic AMP to a different molecule. Which of the following best predicts the effect of inhibiting cyclic AMP phosphodiesterase in a muscle cell stimulated by epinephrine? A.) The concentration of cyclic AMP will decrease because adenylyl cyclase will no longer be activated. B.) The G protein will diffuse out of the cell because it will no longer bind to the plasma membrane. C.) Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated. D.) Glycolysis will stop because epinephrine signaling will no longer stimulate glycogen breakdown.

Answer - C.) Phosphorylase kinase will remain active because protein kinase A will no longer be deactivated.

APC Question: 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? A.) The yeast cells will transition out of G0 but will fail to complete the G1 phase. B.) The yeast cells will initiate mitosis but will fail to complete the G2 phase. C.) The yeast cells will replicate their chromosomes but will fail to complete cytokinesis. D.) The yeast cells will replicate their organelles but will fail to complete the S phase.

Answer - C.) The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.

APC Question: What is the expected percent change in the DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1 phase to the end of the G2 phase? A.) -100% B.) -50% C.) +50% D.) +100%

Answer - D.) +100%

APC Question: 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. 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? A.) 5% B.) 35% C.) 50% D.) 95%

Answer - D.) 95%

APC Question: The relative amount of DNA in a cell at various stages of the cell cycle is shown in Figure 1. Which of the following best describes how the amount of DNA in the cell changes during M phase? A.) The amount of DNA doubles as the DNA is replicated. B.) The amount of DNA slightly increases as a result of new organelle synthesis. C.) The amount of DNA does not change while the cell grows. D.) The amount of DNA is halved as the cell divides into two daughter cells.

Answer - D.) The amount of DNA is halved as the cell divides into two daughter cells.

APC Question: 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? A.) The environment already contains cancer cells. B.) The environment has an abundance of nutrients. C.) The environment lacks signals that would otherwise tell the cell to stop dividing. D.) The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

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