Exam 2 PQs

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Mod 2 Class 1 Practice Questions What does consanguineous marriage do to diversity? Why is this the case? I. Promotes diversity II. Prevents diversity III. Has no effect on diversity IV. Shifts the equilibrium of new and old mutants Which functions promote genetic diversity? I. Homologous Recombination II. Deleterious Loss-of-Function Mutations III. Lethal Gain-of-Function Mutations IV. Independent Assortment a. I,II,IV b. II,III c. IV d. I,IV e. II,III,IV f. None of the above Which statement is FALSE? I. Somatic cells under-go mitosis to form the body II. Somatic cells produce genetically identical daughter cells III. Germ-line cells under-go mitosis to form gametes IV. Germ-line cells produce genetically unique daughter cells V. Somatic cells and Germ-line cells are required for sexual reproduction Which statement is TRUE? I. Sister chromatids separate by cohesion degradation in meiosis I II. Bivalents form after homologous recombination during meiosis I III. Tension from the kinetochore is balanced out by the chiasmata IV. Axial cores maintain chromosome structure on the metaphase plate V. None of the above Which statement is FALSE?

I. The Law of Independent Assortment states that alleles can segregate independently of one another II. Wild-Type phenotypes are indicative of dominant alleles III. Mutations can cause proteins to either lose or gain new functions. IV. You can be phenotypically wild-type, while genotypically mutant. V. None of the above When genotyping your family, you notice that your siblings have haplotype blocks different from your parents but like you. What is the most likely cause? I. Recombination events upon gamete formation generated a new chunk of polymorphisms II. Your mother is not your biological mother III. Your father is not your biological father IV. Your parents are not your biological parents V. Recessive mutations from both parents occur in the same genes After feeding your mice mutagenic food for 3 weeks, you notice their offspring are all phenotypically normal. In the footsteps of Mendel, you breed the offspring amongst each other and find that some of the mice are now sterile and will no longer reproduce. What type of pattern is this most likely to be? I. Homozygous, monogenic, recessive mutation II. Homozygous, monogenic, dominant mutation III. Heterozygous, monogenic, dominant mutation IV. Heterozygous, monogenic, recessive mutation V. A multigenic disease Ch 16 Practice Questions 1. Which of the following statements is TRUE? a. Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. b. The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. c. Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. d. The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells. 2. Which of the following statements is TRUE? a. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. b. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. c. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. d. Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type.

3. The following happens when a G-protein-coupled receptor activates a G protein. a. The β subunit exchanges its bound GDP for GTP. b. The GDP bound to the α subunit is phosphorylated to form bound GTP. c. The α subunit exchanges its bound GDP for GTP. d. It activates the α subunit and inactivates the βγ complex. 4. You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells? a. addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive b. addition of a drug that prevents GTP hydrolysis by Gα c. addition of a drug that activates adenylyl cyclase d. addition of a drug that mimics the ligand of ERC1 5. The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by a. activating a G protein. b. activating a receptor tyrosine kinase. c. diffusing into cells and stimulating the cyclase directly. d. activating an intracellular protein kinase. 6. The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? a. a mutation that prevents dimerization of the receptor b. a mutation that destroys the kinase activity of the receptor c. a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor d. a mutation that prevents the binding of the normal extracellular signal to the receptor 7. A protein kinase can act as an integrating device in signaling if it a. phosphorylates more than one substrate. b. catalyzes its own phosphorylation. c. is activated by two or more proteins in different signaling pathways. d. initiates a phosphorylation cascade involving two or more protein kinases. 8. Which of the following statements is TRUE? a. MAP kinase is important for phosphorylating MAP kinase kinase. b. PI 3-kinase phosphorylates a lipid in the plasma membrane. c. Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP. d. Dimerization of GPCRs leads to Gα activation. 9. When Ras is activated, cells will divide. A dominant-negative form of Ras clings too tightly to GDP. You introduce a dominant-negative form of Ras into cells that also have a

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normal version of Ras. Which of the following statements is TRUE? a. The cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate Ras. b. The cells you create will run out of the GTP necessary to activate Ras. c. The cells you create will divide more frequently compared to normal cells in response to the extracellular signals that typically activate Ras. d. The normal Ras in the cells you create will not be able to bind GDP because the dominant-negative Ras binds to GDP too tightly. 10. The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000 -dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be TRUE? a. Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. b. Glial cells do not have a receptor for QGF. c. QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. d. Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF Ch 18 Practice Questions 1. Which of the following events does NOT usually occur during interphase? a. Cells grow in size. b. The nuclear envelope breaks down. c. DNA is replicated. d. The centrosomes are duplicated. 2. In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? a. at the transition between G1 and S b. when cells enter G0 c. during M d. at the end of G2 FEEDBACK: Cells will check whether the DNA is fully and correctly replicated at the end of G. It does not make sense to monitor DNA replication before S phase because DNA replication has not yet occurred. When cells enter G0, they do not replicate their DNA. During M phase, chromosomes are condensed for chromosome segregation, so it would be difficult for the cell to examine the replicated DNA for errors at that point. 3. Which of the following statements about the cell cycle is FALSE? a. Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells. b. An unfavorable environment can cause cells to arrest in G1.

c. A cell has more DNA during G2 than it did in G1. d. The cleavage divisions that occur in an early embryo have short G1 and G2 phases. 4. Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2? a. The cell would be unable to enter M phase. b. The cell would be unable to enter G2. c. The cell would enter M phase under conditions when normal cells would not. d. The cell would pass through M phase more slowly than normal cells. FEEDBACK: Normal cells arrest at the G2 checkpoint if DNA replication is incomplete or DNA is damaged. Cells without this mechanism may enter M phase with unreplicated or damaged DNA, whereas normal cells would not. 5. Progression through the cell cycle requires a cyclin to bind to a Cdk because a. the cyclins are the molecules with the enzymatic activity in the complex. b. the binding of a cyclin to Cdk is required for Cdk enzymatic activity. c. cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle. d. without cyclin binding, a cell-cycle checkpoint will be activated. FEEDBACK: Cdks require cyclins for enzymatic activity. Cyclins have no enzymatic activities themselves, and cyclin binding to Cdk activates the Cdk. As far as we know, cyclin–Cdk binding is not directly monitored by checkpoints. Ch 19 Practice Questions 1. Organisms that reproduce sexually a. must be haploid, unlike organisms that reproduce asexually. b. can reproduce only with a partner that carries the same alleles. c. create zygotes that are genetically identical to each other. d. undergo a sexual reproductive cycle that involves an alternation of haploid cells with the generation of diploid cells. 2. Which of the following statements is FALSE? a. Asexual reproduction typically gives rise to offspring that are genetically identical. b. Mutations in somatic cells are passed on to individuals of the next generation. c. Sexual reproduction allows for a wide variety of gene combinations. d. Gametes are specialized sex cells. 3. Which of the following statements about the benefits of sexual reproduction is FALSE? a. Sexual reproduction permits enhanced survival because the gametes that carry alleles enhancing survival in harsh environments are used preferentially during fertilization. b. Unicellular organisms that can undergo sexual reproduction have an increased ability to adapt to harsh environments. c. Sexual reproduction reshuffles genes, which is thought to help species survive in novel or varying environments. d. Sexual reproduction can speed the elimination of deleterious alleles. 4. During sexual reproduction, novel mixtures of alleles are generated. This is because

a. in all diploid species, two alleles exist for every gene. b. a diploid individual has two different alleles for every gene. c. every gamete produced by a diploid individual has several different alleles of a single gene. d. during meiosis, the segregation of homologs is random such that different gametes end up with different alleles of each gene. 5. Imagine meiosis in a diploid organism that only has a single chromosome. Like most diploid organisms, it received one copy of this chromosome from each of its parents and the two homologs are genetically distinct. If only a single homologous recombination event occurs during meiosis, which of the following choices below correctly describes the four gametes formed? a. None of the gametes will contain chromosomes identical to the chromosomes found in the original diploid cell. b. All four of the gametes will have chromosomes identical to the chromosomes found in the original diploid cell. c. Three of the gametes will have chromosomes identical to the chromosomes found in the original diploid cell, while one of the gametes will have chromosomes that are different. d. Two of the gametes will have chromosomes identical to the chromosomes found in the original diploid cell, while two of the gametes will have chromosomes that are different. 6. In the absence of recombination, how many genetically different types of gametes can an organism with five homologous chromosome pairs produce? a. 5 b. 10 c. 32 d. 64 7. Which of the following statements most correctly describes meiosis? a. Meiosis involves two rounds of DNA replication followed by a single cell division. b. Meiosis involves a single round of DNA replication followed by four successive cell divisions. c. Meiosis involves four rounds of DNA replication followed by two successive cell divisions. d. Meiosis involves a single round of DNA replication followed by two successive cell divisions. 8. During recombination a. sister chromatids undergo crossing-over with each other. b. chiasmata hold chromosomes together. c. one crossover event occurs for each pair of human chromosomes. d. the synaptonemal complex keeps the sister chromatids together until anaphase II. 9. After the first meiotic cell division, a. two haploid gametes are produced. b. cells are produced that contain the same number of chromosomes as somatic

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cells. c. the number of chromosomes will vary depending on how the paternal and maternal chromosomes align at the metaphase plate. d. DNA replication occurs. 10. What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only? a. The cells would not be able to replicate their DNA. b. The mitotic spindle could not assemble. c. The cells would get larger and larger. d. The cells produced would get smaller and smaller. Ch 17 and Ch 20 Practice Questions 1. Which of the following statements about the cytoskeleton is FALSE? a. The cytoskeleton is made up of three types of protein filaments. b. The cytoskeleton controls the location of organelles in eukaryotic cells. c. Covalent bonds between protein monomers hold together cytoskeletal filaments. d. The cytoskeleton of a cell can change in response to the environment. FEEDBACK: The protein monomers of the cytoskeleton are held together by noncovalent interactions between the protein monomers. All the other statements are true. 2. Intermediate filaments help protect animal cells from mechanical stress because filaments a. directly extend from the interior of the cell to the extracellular space and into the next cell, linking one cell to the next, helping to distribute locally applied forces. b. in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells. c. remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components. d. make up the desmosome junctions that connect cells; these junctions are more important than the internal network of filaments for protecting cells against mechanical stress. FEEDBACK: Intermediate filaments do not directly extend from cell to cell. The linking of intermediate filaments to other cytoskeletal elements (like actin) is thought to help protect cells from mechanical stress. Desmosome junctions are made up of many different kinds of proteins, including cadherins in the extracellular space (which mediate cell–cell adhesion) as well as proteins within the cytoplasm that mediate the attachment of desomosomes to intermediate filaments. These junctions alone are not sufficient for protection against mechanical stress and need the interaction with the intermediate filament network in the cell. 3. Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments? a. They strengthen cells against mechanical stress.

b. Dimers associate by noncovalent bonding to form a tetramer. c. They are found in the cytoplasm. d. Phosphorylation causes disassembly during every mitotic cycle. FEEDBACK: Keratins, neurofilaments, and vimentins are cytoplasmic intermediate filaments, which tend to be very stable once formed. The nuclear intermediate filaments are disassembled and reformed during mitosis; this process is regulated by phosphorylation. 4. Which of the following statements about the structure of microtubules is FALSE? a. Microtubules are built from protofilaments that come together to make a hollow structure. b. The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end. c. Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity. d. α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments. FEEDBACK: α-Tubulin and β-tubulin bind with each other through noncovalent interactions. 5. The microtubules in a cell form a structural framework that can have all the following functions except which one? a. holding internal organelles such as the Golgi apparatus in particular positions in the cell b. creating long, thin cytoplasmic extensions that protrude from one side of the cell c. strengthening the plasma membrane d. moving materials from one place to another inside a cell FEEDBACK: One function of actin filaments, but not microtubules, is to provide a meshwork beneath the plasma membrane that helps to form and strengthen this membrane. Microtubules have all of the other functions that are listed. 6. Which of the following statements regarding dynamic instability is FALSE? a. Each microtubule filament grows and shrinks independently of its neighbors. b. The GTP cap helps protect a growing microtubule from depolymerization. c. GTP hydrolysis by the tubulin dimer promotes microtubule shrinking. d. The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end. FEEDBACK: A newly dissociated tubulin dimer will be bound to GDP; this GDP will need to be exchanged for GTP before it can be added to a newly growing microtubule. 7. Which of the following statements about organellar movement in the cell is FALSE? a. Organelles undergo saltatory movement in the cell. b. Only the microtubule cytoskeleton is involved in organellar movement. c. Motor proteins involved in organellar movement use ATP hydrolysis for energy. d. Organelles are attached to the tail domain of motor proteins. FEEDBACK: Both the actin cytoskeleton and the microtubule cytoskeleton are involved in

organellar movement. 8. Which of the following statements about the movement of materials in a nerve axon is TRUE? a. Movement along microtubules in the axon is slower than free diffusion, but necessary due to the importance of directional transport. b. The small jerky steps seen when vesicles move along microtubules are due to the shrinkage of microtubules that occurs when axonal microtubules undergo dynamic instability. c. Microtubules within an axon are arranged such that all microtubules point in the same direction with their minus ends toward the nerve cell body. d. Microtubules within the axon support the unidirectional motion of materials from the nerve cell body to the axon terminal, while materials transported back from the axon terminal to the cell body move along intermediate filaments. FEEDBACK: Movement along microtubules is faster than free diffusion. The microtubules within the axon are typically stabilized and not undergoing dynamic instability. The saltatory movement of the cargo is due to the properties of the motor proteins that transport the cargo along microtubule tracks. Movement in axons is bidirectional. 9. Which of the following items is not important for flagellar movement? a. sarcoplasmic reticulum b. ATP c. Dynein d. Microtubules FEEDBACK: The sarcoplasmic reticulum is important for muscle contraction. All other items are important for flagellar movement. 10. For both actin and microtubule polymerization, nucleotide hydrolysis is important for a. stabilizing the filaments once they are formed. b. increasing the rate at which subunits are added to the filaments. c. promoting nucleation of filaments. d. decreasing the binding strength between subunits on filaments. FEEDBACK: ATP hydrolysis in actin polymerization decreases the binding strength between monomers in the actin filaments; GTP hydrolysis during tubulin polymerization decreases the binding strength between the tubulin subunits in the microtubule.

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