Test 2A Past Paper Questions PDF

1) Which of the following results in the Meselson-Stahl experiment would support the semiconservative rather than the dispersive model of DNA replication? A. In the first generation of replication after transfer from 15N to 14N medium the DNA was of intermediate density. B. In the first gener...

1) Which of the following results in the Meselson-Stahl experiment would support the semiconservative rather than the dispersive model of DNA replication? A. In the first generation of replication after transfer from 15N to 14N medium the DNA was of intermediate density. B. In the first generation of replication after transfer from 15N to 14N medium the DNA was of heavy density. C. In the first generation of replication after transfer from 15N to 14N medium the DNA, after denaturation, was half heavy density and half light density. D. In the second generation of replication after transfer from 15N to 14N medium the DNA was half intermediate density and half light density. E. C and D both supported the semiconservative model rather than the dispersive model. 2) Which of the following is (are) NOT true about DNA synthesis? A. The DNA polymerase adds deoxyribonucleotides to the 3' end of the newly synthesized strand. B. The DNA polymerase cleaves two phosphates from the 3' end of the newly added deoxyribonucleotide as it is added during DNA synthesis. C. The addition of a deoxyribonucleotide to the newly synthesized strand is facilitated if it base pairs correctly with the template strand. D. If base pairing is not correct after addition of a deoxyribonucleotide the polymerase usually cleaves the phosphodiester bond of the added deoxyribonucleotide and repeats the addition. E. All of the above (A, B, C and D) are correct (no false statements). 3) Which strand is the LAGGING strand in the image below? A. A B. B C. C D. D E. A and B are both lagging strands. PAGE 3, FORM A 4) What does the DNA polymerase that initiates the synthesis of Okazaki fragments use as a primer to initiate the synthesis of the Okazaki fragment? A. The 3’ end of the Okazaki fragment synthesized before it B. The 3’ end of the Okazaki fragment synthesized after it C. An RNA molecule D. The 5’ end of the Okazaki fragment synthesized before it E. It does not need a primer. 5) During proofreading by DNA polymerase, a deoxyribonucleotide base that is incorrectly base-paired with the template strand A. Is removed before it is added to the newly synthesized strand. B. Is removed after it has been added to the newly synthesized strand. C. Is removed from the 3’ end of the newly synthesized strand. D. A and C are both correct E. B and C are both correct. 6) Which of the following enzymes does NOT require a primer to begin synthesis? A. DNA polymerase B. A primase C. A telomerase D. A and C are both correct. E. B and C are both correct. PAGE 4, FORM A 7) Which of the following arrows points to the SLIDING CLAMP? A. A B. B. C. C. D. D. E. E. 8) (1) adds DNA to the lagging strand template at the ends of chromosomes to lengthen the ends, and it uses (2) as a template for the synthesis of complementary DNA in the lagging strand template. A. Telomerase (1), the lagging strand (2). B. Telomerase (1), the lagging strand template (2). C. DNA polymerase (1), the lagging strand (2) D. DNA polymerase (1), the lagging strand template (2) E. Telomerase (1), RNA (2) 9) Which of the following DNA damage events could involve the conversion of a cytosine to a uracil? A. Deamination B. Thymine dimer formation C. Mismatch synthesis D. a double-stranded break in the DNA E. Depurination PAGE 5, FORM A 10) Which of the following enzymes is NOT found in any repair mechanism involved in the repair of a damaged or incorrectly added base during DNA synthesis in a single strand of double helical DNA? A. An enzyme that recognizes the damaged base and excises a region of the strand that contains the base. B. An enzyme that recognizes the damaged base and excises part of the other strand that is complementary to the damaged strand. C. DNA ligase D. A DNA polymerase that resynthesizes the region of DNA damage, using the other undamaged strand as template. E. A protein that recognizes the template strand because it contains a modification that newly synthesized DNA does not contain. 11) In homologous recombination, what is the nature of the strand that provides the initial template for the resynthesis of the DNA in the region that has the double-stranded break? A. The 3’ end of a strand of the damaged DNA B. The 5’ end of a strand of the damaged DNA C. The DNA in the unbroken chromosome that is complementary to the invading 3’ end of the broken chromosome D. The DNA in the unbroken chromosome that has the same sequence as the invading 3’ end of the broken chromosome E. The 3’ and 5’ ends of a strand of the damaged DNA 12) Which of the following does NOT include a glycerol molecule with fatty acids attached? A. Phosphatidylcholine B. Cholesterol C. Triacylglycerol D. Phosphatidylserine E. All of the above (A, B, C and D) contain glycerol. 13) Which of the following is NOT produced by the self-organizing properties of amphipathic membrane phospholipids, in the absence of any proteins? A. spontaneous formation of enclosed lipid vesicles B. spontaneous repair of tears in the membranes C. constant movement of membrane lipid molecules from one layer of the lipid bilayer to the other layer of the lipid bilayer D. The organization of the lipid bilayer, with hydrophilic heads pointed towards the water and two layers of fatty acid tails on the inside E. All of the above (A, B, C and D) are produced. PAGE 6, FORM A 14) You INCREASE the temperature of a bacterium from 20oC to 30oC. How might the organism respond to maintain constant fluidity in its plasma membrane (same at 30oC as at 20oC)? A. Increase the number of unsaturated fatty acid tails in its membrane B. Increase the number of saturated fatty acid tails in its membrane C. increase the length of the fatty acid tails in its membrane D. A and C are both correct. E. B and C are both correct. 15) Which of the following is (are) true? A. Lipids extensively modified with sugars in the Golgi apparatus are not typically moved to the cytosolic side by flippases. B. Flippases hydrolyze ATP to selectively transfer lipids from the exterior (lumenal) side of the Golgi membrane to the cytosolic side. C. Scramblases hydrolyze ATP to selectively transfer lipids from the cytosolic side of the Golgi membrane to the lumenal side. D. A and B are both correct E. B and C are both correct. 16) The protein shown is in the Golgi apparatus. The protein part outside the Golgi and shown as the part of the green rod labeled “membrane glycoprotein” would end up A. on the cytosolic side of the vesicle that is forming and the cytosolic side of the plasma membrane. B. on the cytosolic side of the vesicle that is forming and the extracellular side of the plasma membrane. C. on the lumenal side of the vesicle that is forming and the cytosolic side of the plasma membrane. D. on the lumenal side of the vesicle that is forming and the extracellular side of the plasma membrane. E. on the cytosolic side of the vesicle that is forming and the lumenal side of the endoplasmic reticulum. PAGE 7, FORM A 17) A beta barrel sheet pore that transfers hydrophilic substances from one side of the membrane to the other would have A. hydrophilic residues facing the membrane and hydrophobic residues facing the inside of the barrel. B. hydrophilic residues facing the membrane and hydrophilic residues facing the inside of the barrel. C. hydrophobic residues facing the membrane and hydrophilic residues facing the inside of the barrel. D. hydrophobic residues facing the membrane and hydrophobic residues facing the inside of the barrel. E. alpha helices spanning the membrane, with hydrophilic residues facing the membrane and hydrophobic residues facing the pore. 18) Which one of the following would most likely be extracted from a membrane by increasing the salt concentration in the medium surrounding the membrane? A. an integral membrane protein spanning the membrane with two alpha helices B. an integral membrane protein embedded in only one of the two bilayers C. an integral membrane protein inserted into the membrane with a lipid tail D. a protein spanning the membrane with one alpha helix E. a peripheral membrane protein 19) Which of the following is NOT true about detergent molecules? A. They are amphipathic molecules – polar or charged at one end and nonpolar at the other end. B. They usually contain more than one long fatty acid tail. C. They can form single layer structures called micelles. D. They can break down and solubilize lipid membranes E. They can solubilize membrane proteins. 20) In the Fluorescence Recovery After Photo-bleaching (FRAP) procedure, a non-tethered protein (i.e., one that is NOT attached to another protein and is mobile) is one which A. Produces rapid recovery of its fluorescence photo-bleached from an area of the cell. B. Produces slow recovery or no recovery of its fluorescence photo-bleached from an area of the cell. C. Is rapidly removed from an area of the cell by photo-bleaching D. Is slowly removed from an area of the cell by photo-bleaching E. Does not mix with a differently labeled protein when cells expressing each protein are fused during FRAP PAGE 8, FORM A 21) Which of the following is the LARGEST assembly unit of an intermediate filament that HAS polarity (one end is different from the other end)? A. The intermediate filament monomer B. The intermediate filament dimer C. The intermediate filament tetramer D. The lateral association of 8 tetramers E. The fully assembled intermediate filament 22) Intermediate filaments help protect animal cells from mechanical stress because they 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. remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components. C. in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells. 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. E. are not connected to any cell junctions. 23) An accessory protein that connects intermediate filaments to other cytoskeletal filaments is A. Keratin B. Lamin C. Vimentin D. Neurofilament E. Plectin 24) What type of protein is typically exposed at the NEGATIVE (-) end of a growing microtubule? A.  tubulin B.  tubulin C.  tubulin D. centriolin E. None of the above (A, B, C or D) is exposed at the negative end. 25) Microtubules typically disassemble in an event termed “catastrophe” at A. the positive end when the tubulin dimers at this end are bound with GTP. B. the positive end when the tubulin dimers at this end are bound with GDP. C. the negative end when the tubulin dimers at this end are bound with GTP. D. the negative end when the tubulin dimers at this end are bound with GDP. E. in the middle of the microtubule when the dimers there are bound with GTP. PAGE 9, FORM A 26) Consider a solution that contains some microtubules as well as some unassembled alpha/beta tubulin heterodimers. What would happen if you add a solution that contains no GTP or GDP but only a high concentration of an analog that is similar to GTP and can be bound instead of GTP by the heterodimer, but cannot be hydrolyzed? A. The microtubules will exhibit dynamic instability – sometimes growing, sometimes shrinking. B. The microtubules will shrink until all tubulin heterodimers are in the unassembled state. C. The microtubules will stop growing but will not shrink either. D. The microtubules will continue to grow until all free tubulin subunits have been used up. E. None of the above (A, B, C or D) is the correct answer. 27) You attach DYNEIN molecules by their tails at random orientations to a glass slide, and then add stably assembled microtubules to the glass slide. What will happen? A. The microtubules will not move. B. The microtubules will move back and forth, first in one direction and then in the opposite direction. C. Some microtubules will be severed somewhere in the middle, as dynein motors pull them in opposite directions. D. The microtubules will move in the direction of their + ends (+ ends move further in the + direction). E. The microtubules will move in the direction of their – ends (- ends move further in the – direction). 28) What protein converts the motion of microtubules in a cilium from a sliding to a bending movement? A. the dynein motor B. The kinesin motor C. The linker protein D. The central singlet microtubule E. None of the above (A, B, C or D) 29) Actin filaments A. are assembled from two different types of monomers (alpha and beta) in a single strand of the filament, and filaments are formed from helices of two strands. B. are assembled from a single type of monomer in a single strand of the filament that has no polarity, and filaments are formed from helices of two strands. C. are assembled from a two different types of monomers (alpha and beta) in a single strand, and filaments consist of single strands. D. are assembled from a single type of monomer that all point in the same direction in a single strand of the filament, and filaments are formed from helices of two strands. E. are assembled from a single type of monomer that all point in the same direction in a single strand, and filaments are formed from a single strand. PAGE 10, FORM A 30) In vivo, actin filaments are A. typically assembled as ATP-bound actin is added at the positive end and disassembled as ADP bound actin is removed from the negative end. B. typically assembled as ATP-bound actin is added at the positive end and disassembled as ATP bound actin is removed from the negative end. C. typically assembled as ATP-bound actin is added at the negative end and disassembled as ADP bound actin is removed from the positive end. D. typically assembled as ATP-bound actin is added at the negative end and disassembled as ATP bound actin is removed from the positive end. E. typically assembled as ATP-bound actin is added at the positive end and disassembled as ADP bound actin is removed from the positive end. 31) Which of the following proteins can cause actin filaments to form at a branch point on another actin filament? A. thymosins B. actin-related proteins (ARPs) C. profilins D. B and C are both correct. E. A and B are both correct. 32) In which state of the myosin cycle on actin does myosin bind to unhydrolyzed ATP? A. Released B. Attached C. Cocked D. Force generating E. In all of the above (A, B, C or D); different ones for different molecules. 33) Which of the following changes takes place when a skeletal muscle contracts? A. Z discs move closer together. B. Actin filaments contract. C. Myosin filaments contract. D. Myosin filaments move towards the negative ends of actin filaments. E. Sarcomeres become longer. PAGE 11, FORM A  34) The movement of which protein over the surface of the actin filament in response to Ca++ binding by another protein exposes the myosin binding sites on actin filaments in muscle? A. Tropomyosin B. Troponin C. Receptors in the sarcoplasmic reticulum D. Calsequestrin E. Z disc protein 35) Place the different phases of the cell cycle in correct order. Since the cell cycle is circular, the starting point is arbitrary. A. S, G1, M, G2 B. S, G2, M, G1 C. M, G1, G2, S D. M, G2, G1, S E. G1, G2, M, S 36) At what checkpoint would a cell decide whether to initiate the cell cycle because the environment is favorable for cell division? A. The G2/M checkpoint B. The M Checkpoint C. The G1 START checkpoint D. The APC checkpoint E. It could initiate the cell cycle at any of these checkpoints. 37) Which of the following ACTIVATES the kinase activity of Cdk? A. addition of two phosphates to Cdk B. degradation of a cyclin C. synthesis of a Cdk inhibitor D. The activity of the Cdc25 phosphatase E. All of the above (A, B, C or D) activate the activity of Cdk, so no answer is correct. 38) Which of the following STOPS the activity of a cyclin-dependent kinase (Cdk) that has been active up until this event? A. Phosphorylation of two amino acids on the Cdk B. Dephosphorylation of two amino acids on the Cdk C. Ubiquitinylation and degradation of the cyclin D. Degradation of a Cdk inhibitor E. All of the above (A, B, C or D) are sometimes used for this purpose. PAGE 12, FORM A 39) When Retinoblastoma protein (Rb) is (1), it (2) to activate transcription of a gene that leads to cell cycle (3) A. phosphorylated (1), binds to a promoter (2), arrest (3) B. dephosphorylated (1), binds to a promoter (2), progression (3) C. phosphorylated (1), releases a transcription factor (2), progression (3) D. phosphorylated (1), releases a transcription factor (2), arrest (3) E. dephosphorylated (1), releases a transcription factor (2), progression (3) 40) The phase of mitosis during which the nuclear membrane breaks down and microtubules begin to attach to chromosomes is A. anaphase. B. prophase. C. telophase. D. prometaphase E. metaphase. 41) Which of the following is true about the regulation produced by M-Cdk? A. An activating kinase phosphorylates M-Cdk only after cyclin levels have accumulated, and this phosphorylation leads to immediate activation of the M-Cdk. B. The enzymatic activity of Cdc25 phosphatase is turned off only after cyclin has accumulated. C. Cyclin must be degraded before M-Cdk becomes active to initiate M phase. D. Lots of Cdc25 phosphatase is activated quickly by M-Cdk after some of this M-Cdk has been activated, and this newly activated Cdc25 dephosphorylates an inhibitory site in other M- Cdk molecules to activate them. E. All of the above (A, B, C and D) are true. 42) Centrosomes A. Duplicate during S/G2. B. Nucleate nonkinetochore microtubules. C. Nucleate kinetochore microtubules. D. Nucleate aster microtubules. E. All of the above (A, B, C and D) are true. 43) Which of the following is (are) degraded as a result of the Anaphase Promoting Complex (APC) during mitosis? A. M-cyclin B. Cohesins C. Separase D. A and B are correct but not C. E. A, B and C are all correct. PAGE 13, FORM A 44) Caspases become activated when A. their peptide bonds are cleaved. B. they bind to Bax C. they bind to Bak D. they bind to Bcl2 E. Any of the above (A, B, C or D) can activate caspases. 45) Which off the following is NOT part of an apoptosis inducing pathway? A. Release of cytochrome C from the mitochondrial intermembrane space B. Assembly of the apoptosome C. Degradation of the apoptosome and binding of the degradation products to an initiator caspase D. Activation of an initiator caspase E. All of the above (A, B, C and D) are parts of this pathway. 46) Cell survival rather than apoptosis is promoted (increased) when A. transcription of the Bcl2 gene is increased in response to signaling from survival factor receptors. B. The activities of Bax and Bak are stimulated. C. The activities of Bax and Bak are inhibited. D. A and B increase cell survival. E. A and C increase cell survival. 47) Myostatin A. inhibits the growth and proliferation of muscle cell precursors. B. promotes the growth and proliferation of muscle cell precursors. C. leads to enhanced production of muscles in mutants that eliminate its function. D. A and C are both correct E. B and C are both correct 48) Fill in bubble A to indicate your test form. PAGE 14, FORM A