Biology of the Cell Ch 16-19
Oncogenic conversion of the two dimerizing proto-oncogene components of the AP-1 transcription factor can lead to abnormal cell proliferation. Which of the following two gene products form the active AP-1 transcription factor complex? a. Fos and Jun b. Fos and Myc c. Myc and Jun d. Raf and Myc
Correct Answer: a
SH2 domains are a. protein domains that bind phosphotyrosine-containing peptides. b. the domains on receptor protein-tyrosine kinases that contain the phosphorylated tyrosine. c. domains that mediate the dimerization of receptor protein-tyrosine kinases. d. the domains on receptor protein-tyrosine kinases that possess the kinase activity.
Correct Answer: a A Feedback: Proteins containing SH2 domains are the first downstream targets of receptor protein-tyrosine kinases.
Which of the following is not a therapeutic effect of aspirin? a. Stimulation of the growth of fibroblasts at the site of a wound, thus aiding the healing process b. Reduction of inflammation and pain c. Reduction of blood clotting d. Reduction of the chance of acquiring colon cancer
Correct Answer: a Answer A Feedback: A substance stored in blood platelets, platelet-derived growth factor (PDGF), has this effect.
Which of the following are not phosphorylated by the Cdk1/cyclin B complex during mitosis? a. Histone H3 b. Golgi matrix proteins c. Nuclear lamins d. Condensins
Correct Answer: a Answer A Feedback: Although histone H3 is phosphorylated during mitosis, the kinase has not yet been identified.
Which of the following steroid hormone(s) is/are not secreted by the gonads? a. Corticosteroids b. Progesterone c. Estrogen d. Testosterone
Correct Answer: a Answer A Feedback: Corticosteroids, which include glucocorticoids and mineralocorticoids, are secreted by the adrenal gland.
Which of the following stem cells have the capacity to give rise to all the differentiated cell types of adult organisms? a. Embryonic stem cells b. Endothelial cells c. Satellite cells d. Epithelial cells
Correct Answer: a Answer A Feedback: Currently these are the only cells that are known to have this capacity, although scientists continue to learn more about stem cells with other origins.
Most of the effects of cyclic AMP (cAMP) in the cell are mediated by a. protein kinase A. b. ion channels. c. protein kinase C. d. cAMP phosphodiesterase.
Correct Answer: a Answer A Feedback: Cyclic AMP activates protein kinase A, which then stimulates the breakdown of glycogen into glucose, and also alters the pattern of gene expression via activation of the transcription factor CREB.
Cell cycle checkpoints ensure that complete genomes are transmitted to daughter cells. DNA damage checkpoints are found in all of the following phases except a. M phase. b. G1 phase. c. G2 phase. d. S phase.
Correct Answer: a Answer A Feedback: DNA damage checkpoints are not found in M.
In which of the following cell types do G1 and G2 not take place? a. Early embryonic cells b. Budding yeast cells c. Typical proliferating human cells d. Skin fibroblasts
Correct Answer: a Answer A Feedback: Early embryonic cells divide very rapidly, alternating between M and S phases. Since G1 and G2 do not occur, the cell does not have time to grow prior to cell division, and the resulting daughter cells are smaller than the mother cells.
Which of the following diseases would not be an ideal target for therapeutic cloning? a. HIV b. Parkinson's disease c. Spinal cord injury d. Diabetes
Correct Answer: a Answer A Feedback: HIV is caused by a virus and not a cellular mutation or defect
Which of the following genes is expressed by SV40 (simian virus 40) and induces transformation? a. The gene encoding large T antigen b. E1A c. E6 d. E1B
Correct Answer: a Answer A Feedback: Large T and small T are expressed by SV40 and initiate the transformation process.
Most cells in an adult animal are a. in G0, or quiescent, phase. b. actively proliferating. c. stem cells. d. undergoing meiosis.
Correct Answer: a Answer A Feedback: Most adult cells are differentiated and cease proliferating, entering the G0 phase. However, many can reenter the cell cycle and resume proliferation if they are needed to replace damaged tissue.
Which of the following cells cannot develop from hematopoietic stem cells? a. Satellite cells b. Platelets c. B lymphocytes d. Macrophages
Correct Answer: a Answer A Feedback: Satellite cells are the stem cells in skeletal muscle that give rise to new muscle following damage or injury.
Heterotrimeric G proteins are not the only guanine nucleotide-binding proteins. Which of the following also represents a family of GTP-binding proteins that act as monomers instead of being a heterotrimeric compound? a. Ras b. ERK c. Raf d. Smad
Correct Answer: a Answer A Feedback: The members of the Ras family are often called small GTP-binding proteins because they are about half the size of the α subunits of heterotrimeric G proteins.
PTEN is a tumor suppressor gene in the Akt signaling pathway. Which of the following statements about PTEN/Akt is false? a. PIP2 can be oncogenically mutated to induce cell survival. b. PTEN antagonizes (has the opposite effect) of PI 3-kinase. c. Akt can be oncogenically mutated to induce cell survival. d. It is a lipid phosphatase that dephosphorylates PIP3 to PIP2.
Correct Answer: a Answer A Feedback: This is false. PIP2 is not a protein and cannot be mutated.
You perform an experiment by incubating a radiolabeled nucleotide into the medium of a culture of cells. The cells that take up the radiolabel would be expected to be in what phase of the cell cycle? a. S phase b. G1 phase c. G2 phase d. M phase
Correct Answer: a Answer A Feedback: This is the phase in which cells are actively replicating; the radiolabeled nucleotide is incorporated into DNA that is being newly synthesized.
Angiogenesis contributes to cancer development by a. providing nutrients and oxygen to tumors and by facilitating metastasis. b. initiating a mutation in a gene that causes uncontrolled cell growth. c. inhibiting apoptosis (programmed cell death). d. preventing the normal inhibition of growth that occurs between cells on contact.
Correct Answer: a Answer A Feedback: Tumors stimulate angiogenesis, or new blood vessel formation, which brings them nutrients and oxygen. In addition, the blood vessels provide a path of entry into the circulatory system, from which tumors can spread to other tissues.
What is the best rationale for the use of therapeutic cloning to replace defective cells or tissues in a patient? a. The transplanted cells are identical to those of the recipient who donated the adult nucleus, so complications of immune rejection are avoided. b. Embryos do not have to be destroyed, so ethically there is little controversy. c. It is a very efficient process for generating the tissues that need to be replaced. d. We already know how to fully differentiate the embryonic stem cells into all the major cell types.
Correct Answer: a Answer A Feedback: Without question, this is the best argument for therapeutic cloning.
The p21 and p15 proteins are examples of a. Cdk inhibitors. b. cyclins. c. oncogenes. d. growth factors.
Correct Answer: a Answer A Feedback: p15 inhibits Cdk4, 6/cyclin D complexes; p21 inhibits several Cdk/cyclin complexes to block progression of the cell cycle at G1.
The more than 40 oncogenic retroviruses that have been identified share expression of all of the following genes except a. src. b. pol. c. env. d. gag.
Correct Answer: a Answer A Feedback: src is found in some retroviruses, but not all. It encodes a tyrosine kinase.
Receptor protein-tyrosine kinases represent critical molecules involved in growth and differentiation though phosphorylation of target substrates on tyrosine residues. Which of the following is not a common structural feature of all receptor protein-tyrosine kinases? a. An N-terminal extracellular ligand-binding domain b. A single polypeptide c. A cytosolic C-terminal domain with protein-tyrosine kinase activity d. A single transmembrane α helix
Correct Answer: b
Some differentiated cells retain the ability to proliferate as needed to repair damaged tissue throughout the life of the organism. Which of the following cell types do not retain this unique ability? a. Fibroblasts b. Neurons c. Endothelial cells d. Epithelial cells
Correct Answer: b Answer B Feedback: As a rule, neurons do not have the capacity to proliferate when needed.
What is the difference between a benign tumor and a malignant tumor? a. A malignant tumor is painful, and a benign tumor is not. b. A malignant tumor has the ability to spread to other tissues and to initiate tumors at secondary sites, whereas a benign tumor does not spread. c. A benign tumor will cause a less severe form of cancer than a malignant tumor. d. A malignant tumor is caused by a virus, whereas a benign tumor arises spontaneously.
Correct Answer: b Answer B Feedback: Benign tumors do not spread, and they represent better candidates for removal by surgery. Malignant tumors, on the other hand, can spread throughout the body, invading other tissues and organs. They are far more destructive and difficult to treat.
What is the difference between neurotransmitters and neuropeptides? a. Neuropeptides are generated by neuronal cells but do not transmit signals. b. Neurotransmitters are small hydrophilic molecules and neuropeptides are small proteins. c. Neurotransmitters are small protein molecules and neuropeptides are large ones. d. Some neuropeptides can act on distant cells, whereas neurotransmitters cannot.
Correct Answer: b Answer B Feedback: Both neurotransmitters and neuropeptides transmit signals, but they are in different chemical classes
Which of the following products would result from caspase cleavage of a protein with the amino acid sequence AVEELCSTWYYDLLCHMRTL? a. AVEELCS + TWYYDLLCHMRTL b. AVEELCSTWYYD + LLCHMRTL c. AVEELCSTWYYDLLCH + MRTL d. AVEELC + STWYYDLLC + HMRTL
Correct Answer: b Answer B Feedback: Caspases cleave proteins at aspartate residues.
Apoptosis, or programmed cell death, occurs in all of the following cases except a. in virus-infected cells. b. in cells damaged by injury. c. in cells with potentially cancer-causing mutations. d. during the elimination of tissue between the digits in the formation of human fingers.
Correct Answer: b Answer B Feedback: Cells damaged by injury do not die in the distinct manner of cells undergoing apoptosis but by swelling and lysing.
The spindle assembly checkpoint monitors the alignment of chromosomes in the mitotic spindle during mitosis to insure an even distribution of chromosomes to each of the daughter cells. If the chromosomes do not align properly, the spindle assembly checkpoint will arrest cells in what phase of mitosis? a. Prophase b. Metaphase c. Anaphase d. Telophase
Correct Answer: b Answer B Feedback: Chromosomes align on the mitotic spindle during metaphase and if this is misaligned, cell cycle is arrested.
Infection with which of the following viruses is associated with development of liver cancer in humans? a. Simian virus 40 (SV40) b. Hepatitis B viruses c. Epstein-Barr virus d. Papillomaviruses
Correct Answer: b Answer B Feedback: Chronic infection with hepatitis B along with hepatitis C is associated with a hundredfold increase in the risk of acquiring liver cancer.
DNA content can be determined using a method of flow cytometry that can determine 2n or 4n states of cells based on cell counting and fluorescent labeling of DNA. Which of the following phases would be identified through flow cytometry as 2n? a. M phase b. G1 phase c. G2 phase d. S phase
Correct Answer: b Answer B Feedback: G1 cells have yet to replicate and have only a 2n, or diploid, amount of DNA.
In unstimulated cells, NF-κB proteins are maintained in an inactive state in the cytosol by interactions with a. Hedgehog. b. IκΒ. c. adaptor proteins. d. the TNF receptor.
Correct Answer: b Answer B Feedback: In its non-phosphorylated form, IκΒ binds to NF-κB and prevents its translocation to the nucleus.
Integrins are transmembrane proteins that connect a. the nuclear laminae to cytoplasmic kinases. b. the extracellular matrix to the cytoskeleton. c. focal adhesions to hemidesmosomes. d. microtubules to actin filaments.
Correct Answer: b Answer B Feedback: Integrins span the plasma membrane and provide a communication link between the extracellular matrix and the cytoskeleton within the cell.
Interphase is defined as a. the G1 and G2 phases. b. the G1, G2, and S phases. c. G0, the quiescent phase. d. M phase.
Correct Answer: b Answer B Feedback: Interphase is the part of the cell cycle in which the chromosomes are decondensed and spread throughout the nucleus. Cell growth and DNA synthesis take place during interphase, which includes G1, S, and G2, in preparation for mitosis (M phase).
The progression from metaphase to anaphase is triggered by a. activation of protein kinases by MPF. b. ubiquitin-mediated proteolysis of key proteins. c. binding of an inhibitory protein to MPF. d. depolymerization of the mitotic spindle.
Correct Answer: b Answer B Feedback: MPF activates the anaphase-promoting complex, which is a ubiquitin ligase. As a result, key proteins such as Scc1, which links sister chromatids together, and cyclin B are degraded.
Which of the following is not one of the phases of mitosis? a. Prophase b. S phase c. Metaphase d. Anaphase
Correct Answer: b Answer B Feedback: S phase, when the cell's DNA becomes duplicated, occurs before mitosis, during interphase.
At fertilization, the sperm binds to a receptor on the surface of the egg and fuses with the plasma membrane, initiating the development of a new diploid organism. Which of the following statements about fertilization is false? a. Binding of a sperm to its receptor on the egg induces an increase in cytoplasmic calcium. b. The progression of metaphase II to anaphase is triggered by the activation of MPF. c. Eggs are arrested at metaphase II of meiosis and fertilization leads to anaphase progression. d. Once fertilized, secretory vesicles are exocytosed, leading to an alteration in the extracellular coat of the egg to prevent additional sperm entry.
Correct Answer: b Answer B Feedback: The progression of metaphase II to anaphase is triggered by the activation of APC/C.
Which of the following statements about protein kinase A (PKA) is false? a. In the inactive state, PKA exists as a tetramer of two regulatory (R) and two catalytic (C) subunits. b. PKA binds a total of four molecules of cAMP, one on each of the four subunits. c. PKA binds a total of four molecules, two molecules on each of the two regulatory (R) subunits. d. Once activated, the catalytic (C) subunits dissociate and activate target molecules.
Correct Answer: b Answer B Feedback: This is a false statement. The catalytic (C) subunits do not bind cAMP.
Which of the following statements about the tumor suppressor gene p53 is false? a. It plays a role in up to 50% of human cancers. b. It is the cause of the rare childhood cancer of the eye, retinoblastoma. c. It blocks cell cycle progression in response to DNA damage. d. It is required for apoptosis in response to DNA damage.
Correct Answer: b Answer B Feedback: This is false. A gene called Rb is the cause of retinoblastoma.
Which of the following statements about papillomaviruses is false? a. They induce both benign and malignant tumors in humans. b. They have been shown to cause both benign and malignant breast cancer. c. They predominantly infect epithelial cells. d. Upon infection, they cause expression of E6 and E7, which induce transformation.
Correct Answer: b Answer B Feedback: This is false. Papillomaviruses are associated with cervical and other anogenital cancers.
Which of the following statements regarding heterotrimeric G proteins in a resting state is true? a. GDP is bound to the β subunit in a complex with both the α and γ subunits. b. GDP is bound to the α subunit in a complex with both the β and γ subunits. c. GTP is bound to the α subunit in a complex with both the β and γ subunits. d. The proteins are in a complex with G protein-coupled receptors.
Correct Answer: b Answer B Feedback: This is the state of G proteins when in a resting state.
Murine embryonic stem cells are grown in the presence of a growth factor. What growth factor is generally used for this? a. VEGF (vascular endothelial growth factor) b. LIF (leukemia inhibitory factor) c. PDGF (platelet-derived growth factor) d. EGF (epidermal growth factor)
Correct Answer: b Answer B Feedback: Though the name would suggest otherwise, this is the growth factor used almost universally with murine embryonic stem cells.
The following is a signal transduction cascade (with one missing step) initiated by double-stranded DNA damage and ending with activation of apoptosis by the BH3-only proteins PUMA and Noxa: Double-stranded DNA damage; Chk2; _______; PUMA/Noxa; apoptosis. Which protein belongs in the blank space? a. Apaf-1 b. p53 c. Chk1 d. Bax
Correct Answer: b Answer B Feedback: p53 is phosphorylated and stabilized by Chk2, which then goes on to increase transcription of PUMA and Noxa.
People infected with HIV are more susceptible to acquiring certain types of cancer because a. the virus encodes a protein that binds and inactivates the tumor suppressor gene p53. b. these individuals are immunosuppressed. c. the virus integrates into the genome and alters the pattern of expression of adjacent genes. d. of the expression of the viral gene tax.
Correct Answer: b B Feedback: HIV infects immune cells, and thus it results in increased susceptibility to many illnesses, including cancer.
Inhibitors of apoptosis (IAPs) regulate caspases. Which of the following statements about IAPs is false? a. IAPs were discovered in virus-infected insect cells as viral proteins that inhibit apoptosis of the host cell in response to viral infection. b. IAPs target caspases for ubiquitination and degradation in the proteasome. c. IAPs are activated through the p53 pathway. d. IAPs interact directly with caspases.
Correct Answer: c
Which of the following statements is true in reference to Bax and Bak, two members of the Bcl-2 family? a. Bax and Bak are antiapoptotic proteins that function to repress apoptosis in cells. b. Bax and Bak act as ligands to the apoptosome in activation caspases. c. When activated, Bax and Bak form oligomers in the outer membrane of mitochondria, leading to the release of cytochrome c. d. Bax and Bak directly activate caspase-9.
Correct Answer: c
Which of the following has not been found to cause cancer? a. Chemicals b. Radiation c. Bacteria d. Viruses
Correct Answer: c Answer C Feedback: Although bacteria can cause disease, they have not been found to cause cancer.
The term "paracrine signaling" refers to a. signaling between cells located far from each other. b. stimulation of a cell by substances produced by the cell itself. c. signaling between cells located close to each other. d. signaling between parenchyma cells.
Correct Answer: c Answer C Feedback: An example of this is transmission of a nerve impulse between nerve cells.
The Bcl-2 family of proteins is divided into three functional groups that contain and share as many as four Bcl-2 homology domains (BH domains). Which of the following is common to all members of the Bcl-2 family? a. BH1 b. BH2 c. BH3 d. BH4
Correct Answer: c Answer C Feedback: BH3 is found in the proapoptotic BH3-only group and is the only domain found in this group.
Burkitt's lymphoma is caused almost exclusively by a. point mutations in the ras proto-oncogene. b. translocation of the abl proto-oncogene. c. translocation of the c-myc proto-oncogene. d. amplification of the N-myc gene.
Correct Answer: c Answer C Feedback: Burkitt's lymphoma is caused by a translocation of c-myc to one of the immunoglobulin gene loci, causing its unregulated expression.
The MEK kinase (MAP kinase/ERK kinase) is unusual in that it a. is activated by a kinase. b. lies downstream of G protein-coupled receptors. c. is a dual-specificity kinase, having the ability to phosphorylate both threonines and tyrosines. d. activates a kinase.
Correct Answer: c Answer C Feedback: Most kinases can either phosphorylate serines and threonines or tyrosines, but MEK can phosphorylate both a threonine and a tyrosine residue on ERK2.
An example of signaling by direct cell-cell interactions is a. the Wingless (Wnt) signaling pathway. b. the JAK/STAT pathway. c. the Notch pathway. d. the pathway leading to vulval development in C. elegans.
Correct Answer: c Answer C Feedback: Notch is a transmembrane protein that is stimulated by other transmembrane proteins (such as Delta) on adjacent cells.
The G2 cell cycle checkpoint detects a. the binding of the MCM proteins to origins of replication. b. chromosome misalignment. c. unreplicated or damaged DNA. d. levels of p53.
Correct Answer: c Answer C Feedback: The G2 checkpoint ensures that the genome has been entirely replicated and that damaged DNA has been repaired prior to entry into M phase.
The sequence of DNA on each chromosome where the sister chromatids are held together is called the a. centrosome. b. kinetochore. c. centromere. d. centriole.
Correct Answer: c Answer C Feedback: The centromere is a sequence of DNA where the sister chromatids are held together prior to their migration to opposite poles of the spindle.
Pioneering work by Judah Folkman led to a class of anticancer drugs, such as sunitinib and sorafenib. These drugs function by a. inhibiting DNA replication. b. binding and inhibiting the ErbB-2 oncogene protein, which is overexpressed in many breast cancers. c. inhibiting the formation of new blood vessels in the vicinity of the tumor. d. inhibiting farnesylation.
Correct Answer: c Answer C Feedback: These drugs inhibit angiogenesis and thus cut off a tumor's source of nutrients and oxygen, as well as inhibiting the spread of malignant cells to other tissues.
Which of the following statements regarding cyclin D is false? a. It is required for cell cycle progression. b. It is activated by growth factors. c. It is always present and its activity is regulated by fluctuating levels of Cdk4 and Cdk6. d. It is rapidly degraded following removal of appropriate growth factors.
Correct Answer: c Answer C Feedback: This is a false statement about cyclin D. It is not always present, though it does require interaction of Cdk4 and Cdk6.
The PI 3-kinase pathway is important in countering apoptosis in healthy cells and promotes cell survival. Which of the following statements about the PI 3-kinase pathway is false? a. PI 3-kinase is activated by a receptor tyrosine kinase. b. PIP3 activates Akt, a serine/threonine kinase. c. Activated Akt phosphorylates and activates Bad. d. PI 3-kinase phosphorylates PIP2 to form PIP3.
Correct Answer: c Answer C Feedback: This is a false statement. Akt phosphorylates and inactivates Bad. In its nonphosphorylated state, Bad is activated and triggers apoptosis.
Which of the following statements about caspases is false? a. They cleave target proteins after aspartic acid residues in their substrate proteins. b. They inhibit DNAse which, when activated, fragments nuclear DNA. c. They predominantly break up Golgi membranes, which in turn release other caspases to cleave nuclear lamins and cytoskeleton proteins. d. They contain cysteine residues in the active site.
Correct Answer: c Answer C Feedback: This is a false statement. Caspases directly break up nuclear lamins and cytoskeleton proteins.
In reference to stem cells, which of the following statements is false? a. Stem cells divide to form one daughter cell that remains a stem cell and a second cell that proliferates and then differentiates. b. Stem cells are a subpopulation of less differentiated self-renewing cells present in most adult tissues. c. Stem cells in organs can only differentiate into the tissue in which they are located. d. Stem cells in tissues are typically found in G0, unless they are called on to differentiate.
Correct Answer: c Answer C Feedback: This is a false statement. For example, hematopoietic stem cells can differentiate into skin, lung, bone, etc.
The phase of the cell cycle that corresponds to the interval between mitosis and initiation of DNA replication is referred to as the a. M phase. b. S phase. c. G1 phase. d. G2 phase.
Correct Answer: c Answer C Feedback: This is also called gap 1 phase.
Which of the following statements about cancers is false? a. Carcinomas are malignancies of epithelial cells. b. Leukemias are malignancies that arise from blood-forming cells. c. Lymphomas are malignancies from colon tissue. d. Sarcomas are malignancies of connective tissue like muscle and bone.
Correct Answer: c Answer C Feedback: This is false. Lymphomas, like leukemias, are malignancies that arise from blood-forming cells.
Cyclic AMP (cAMP) is synthesized from ATP by the action of a. phosphodiesterase. b. phosphorylase kinase. c. adenylyl cyclase. d. protein kinase A (PKA).
Correct Answer: c Answer C Feedback: This is the key enzyme in cAMP synthesis using ATP as the substrate.
Which of the following is not one of the ways in which oncogenes incorporated into viral genomes can differ from their normal cellular counterparts (proto-oncogenes)? a. They can contain fusions to viral sequences, resulting in structural changes that deregulate the protein. b. They can contain point mutations in regulatory domains, resulting in a loss of protein regulation. c. They can be present in many tandem copies, as opposed to the single copy present in the cell. d. They can be expressed from much stronger promoters than the normal cellular promoter.
Correct Answer: c Answer C Feedback: Viruses have very compact genomes and do not possess tandem copies of genes.
Which of the following is an example of endocrine signaling? a. Epinephrine release by motor neurons at the neuromuscular junction and binding to receptors on adjacent skeletal muscle cells b. Antigen stimulation of T lymphocytes, leading to the stimulation and synthesis of a growth factor that drives their own proliferation c. Insulin release by β cells in the pancreas, mediating an effect of glucose uptake by muscle cells d. None of the above
Correct Answer: c C Feedback: This is classic endocrine signaling: release of a signaling molecule affecting distant target cells, typically carried through the bloodstream.
In yeast, START triggers the progression from G1 to S. Which of the following are involved in regulating START? a. Nutrients b. Mating factors c. Cell size d. All of the above
Correct Answer: d
The PDGF receptor is a proto-oncogene (a normal cellular gene that, when mutated, becomes oncogenic). Which of the following statements about the PDGF receptor is true? a. The oncogenic mutation occurs in the extracellular amino terminal end of the receptors. b. The oncogenic mutation constitutively activates the intracellular kinase activity of the protein. c. The oncogenic mutation generates a receptor that is no longer dependent on ligand for activation. d. All of the above
Correct Answer: d Answer D Feedback: All are true for oncogenic mutations of the PDGF receptor.
Bone marrow transplants are used to treat patients with which of the following diseases? a. Aplastic anemia b. Hemoglobin disorders c. Immune deficiencies d. All of the above
Correct Answer: d Answer D Feedback: All of these diseases are currently being treated with bone marrow transplants, which in effect are hematopoietic stem cell transfers.
TNF and related cytokines can directly induce apoptosis. Which of the following statements about TNF-mediated induction of apoptosis is true? a. TNF binds a trimeric receptor complex on the surface of the cell membrane. b. Upon receptor binding, caspase-8 is activated through an adaptor protein. c. Caspase-8 activates Bid, which in turn activates Bax and Bak and then feeds into the mitochondrial pathway. d. All of the above
Correct Answer: d Answer D Feedback: All of these statements combined describe the TNF apoptotic pathway.
Which of the following tumor suppressor genes has been associated with colon cancer? a. APC b. p53 c. Smad2 or Smad4 d. All of the above
Correct Answer: d Answer D Feedback: All of these, as well as others, have been linked to colon cancer.
Which of the following is not involved in metaphase II arrest during meiosis? a. Cytostatic factor (CSF) b. Mos c. Rsk d. An increase in cytoplasmic calcium levels
Correct Answer: d Answer D Feedback: An increase in cytoplasmic calcium levels does not occur until after fertilization, and it triggers completion of meiosis.
Which of the following events is not associated with apoptosis? a. Fragmentation of chromosomal DNA b. Condensation of chromatin c. Breaking up of the cell nucleus d. Cell cycle reentry
Correct Answer: d Answer D Feedback: Cells do not need to enter cell cycle to undergo apoptosis.
The most lethal type of cancer in the United States is cancer of the a. prostate. b. colon/rectum. c. breast. d. lung.
Correct Answer: d Answer D Feedback: Deaths from lung cancer account for approximately 30% of all cancer deaths in the United States.
he majority of oncogene proteins are a. metabolic enzymes. b. structural proteins, such as nuclear lamins. c. proteins involved in cell sorting. d. components of signaling pathways that regulate cell proliferation.
Correct Answer: d Answer D Feedback: Defective versions of proteins involved in signaling cell proliferation are the most common causative agents of cancer.
During what phase of meiosis does recombination between maternal and paternal chromosomes occur? a. Anaphase I b. S phase c. Prophase II d. Prophase I
Correct Answer: d Answer D Feedback: During prophase I homologous chromosomes are aligned in close proximity to one another, and it is during this phase that crossovers between maternal and paternal chromosomes occur.
In the absence of growth factor, most animal cells will stop the cell cycle at a restriction point in what stage? a. S phase b. M phase c. G2 phase d. G1 phase
Correct Answer: d Answer D Feedback: In the absence of growth factors, cells arrest in G1 and enter G0, remaining quiescent and awaiting a signal such as a growth factor to divide, much like quiescent fibroblasts.
Which of the following hormone(s) is/are not synthesized from cholesterol? a. Testosterone b. Progesterone c. Corticosteroids d. Retinoic acid
Correct Answer: d Answer D Feedback: Retinoic acid is synthesized from Vitamin A.
Which of the following signaling pathways allow for direct cell-cell signaling by transmembrane proteins? a. NF-κB b. Wnt c. Hedgehog d. Notch
Correct Answer: d Answer D Feedback: The Notch receptor on one cell binds the Delta receptor on an adjacent cell, initiating notch signaling.
Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor? a. Receptor dimerization b. Receptor phosphorylation c. Conformational changes in the receptor d. Increased synthesis of the receptor
Correct Answer: d Answer D Feedback: The synthesis of the receptor is not typically increased either at the transcriptional or translational level following binding. In fact, sometimes the degradation of the receptor is stimulated as a step toward returning the cell to the resting state.
Which of the following statements about cyclin B is false? a. It is a component of MPF. b. It accumulates throughout S and G2. c. It activates Cdc2 protein kinase. d. It cycles between active and inactive states in the cell cycle.
Correct Answer: d Answer D Feedback: This is a false statement. Cyclin B protein levels oscillate throughout the cell cycle, but its activity does not change.
Which of the following statements about cloning by somatic cell nuclear transfer is false? a. The nucleus of an adult somatic cell is transferred to an enucleated unfertilized egg. b. Somatic cell nuclear transfer was first carried out in frogs in the 1950s. c. In the laboratory, the cloned egg is cultured to an early embryo stage and then transferred to a foster mother. d. The cloned embryo is genetically identical to the foster mother. .
Correct Answer: d Answer D Feedback: This is a false statement. The embryo is genetically identical to the adult from which the somatic cell nucleus was harvested
G protein-coupled receptors are important molecules involved in signal transduction. Which of the following statements about G protein-coupled receptors is true? a. They are activated only by steroid hormones. b. They bind only guanine nucleotides. c. They bind both adenine and guanine nucleotides. d. They generally contain seven membrane-spanning α helices.
Correct Answer: d Answer D Feedback: This is a structural characteristic of most G protein-coupled receptors.
Which of the following statements concerning the difference between cancer cells and normal cells is false? a. Normal cells display density-dependent inhibition of cell proliferation. b. Cancer cells have reduced requirements for extracellular growth factors. c. Malignant cells generally secrete proteases that digest extracellular matrix components. d. Cancer cells undergo normal differentiation, but excessive proliferation.
Correct Answer: d Answer D Feedback: This is false. Cancer cells do not differentiate normally. In fact, many therapies are designed to push cancer cells toward terminal differentiation where they would be likely to stop proliferating.
Which of the following statements about G protein signaling is false? a. Hormone binding induces an interaction of the receptor with the G protein, stimulating the release of GDP and the exchange of GTP on the α subunit. b. Once activated, the GTP-bound α subunit dissociates from βγ and interacts with its target. c. Activity of the α subunit is terminated by the hydrolysis of GTP to GDP. d. The α subunit becomes deactivated when the hormone dissociates from the receptor.
Correct Answer: d Answer D Feedback: This statement is false. Remember that a hallmark of signal transduction is that the ligand binding to the receptor is what initiates the cascade of events and once initiated can readily dissociate without affecting downstream events.
Which of the following is/are not considered a viable of stem cells? a. Umbilical cord blood b. Bone marrow c. An embryo d. Tumors
Correct Answer: d Answer D Feedback: Tumor cells can be isolated and grown in culture but are not generally thought to be sources of stem cells.
The signaling molecule nitric oxide (NO) functions a. by binding its cell surface receptor and triggering an intracellular signaling cascade. b. by diffusing across the membrane and binding its intracellular receptor, which then activates transcription. c. on cells located far from the cells where it was synthesized. d. by diffusing across the cell membrane and changing the activities of intracellular enzymes.
Correct Answer: d Answer D Feedback: Unlike most signaling molecules, nitric oxide does not bind a receptor but rather directly alters the activity of an enzyme.