front 1 Motor proteins are able to generate force by ___________. | back 1 undergoing a series of conformational changes |
front 2 Why does an actin thin filament manage to move continuously during a contraction cycle? | back 2 All of the myosin heads beat out of synchrony with one another. |
front 3 In what form are proteins and neurotransmitters usually transported down the axon of a nerve cell? | back 3 inside transport vesicles |
front 4 A(n) ________ motor, like muscle myosin (myosin II) and unlike myosin V, remains in contact with its track, in this case the thin filament, for only a small portion, less than 5 percent, of the overall cycle. | back 4 nonprocessive |
front 5 Nucleation of microtubules takes place rapidly inside a cell, where it occurs in association with a variety of specialized structures called _____________. | back 5 All of the provided answers |
front 6 The central, rod-shaped domain of an intermediate filament is flanked on each side by globular domains of variable size and sequence. What structure forms the core of the central, rod-shaped domain? | back 6 alpha-helix |
front 7 EDTA is a chemical that binds to and removes (chelates) divalent cations from solution. Treatment of isolated axonemes with EDTA leads to the removal of the inner and outer arms extending from the A microtubules of the axoneme. Which of the following statements wouls appear to be true based on this information? | back 7 Magnesium ions are required for dynein to bind to the A tubules of the axoneme. |
front 8 Which of the following appears to be the most extensible? | back 8 intermediate filaments |
front 9 What would happen if you cultured a frog embryo just after gastrulation in the presence of cytochalasin? | back 9 The cells of the neural plate elongate normally but do not become constricted as usually happens. |
front 10 The cross-bridges that hold intermediate filaments together are composed of _______. | back 10 plectin |
front 11 Which of the following molecules is a non-diffusible, integral protein of the plasma membrane that binds specifically to its receptor on the surface of the growth cone? This protein acts as a neuronal guidance factor. | back 11 ephrin |
front 12 Toward the end of gastrulation in vertebrates, the ectodermal cells situated along the embryo's dorsal surface elongate and form a tall epithelial layer that is called the _________ | back 12 neural plate |
front 13 Which Microtubule-Organizing Center (MTOC) gives rise to cilia and flagella? | back 13 basal bodies |
front 14 The focal complexes that form near the leading edge of a motile cell exert traction force through their associated __________ and then typically disassemble as the cell moves forward or mature into larger, more contractile focal adhesions. | back 14 actin filaments |
front 15 Which of the following appears to be the most extensible? | back 15 intermediate filaments |
front 16 Treatment of isolated sperm axonemes with 0.6 M NaCl has been shown to remove selectively the outer arms from the A microtubules of the axoneme, leaving the inner arms in place. What would be the most likely effect on the NaCl-treated axoneme when ATP was added to the medium? | back 16 The axonemes would beat at about half the rate of the intact axoneme |
front 17 Structures that move from the cell body of a neuron down the axon toward the neuron terminals are said to move in a(n) _________ direction. radial | back 17 anterograde |
front 18 Which type of cytoskeletal element is described as tough, ropelike fibers composed of a variety of related proteins like keratin? | back 18 intermediate filaments |
front 19 One of the WASP/WAVE family of proteins, specifically WASP, the founding member of the family, is associated with what disease below | back 19 Wiskott-Aldrich syndrome |
front 20 Along which structure do membranous vesicles and organelles typically engage in local movement in the cell periphery of an animal cell? | back 20 microfilaments |
front 21 What is the direct source of energy that powers molecular motors? | back 21 hydrolysis of ATP |
front 22 What motor is associated with microfilaments? | back 22 myosin |
front 23 The first direct measurement of a motor taking single steps was an analysis of ________ stepping using ________. | back 23 kinesin, optical trap technology |
front 24 What happens to the Z lines after contraction of the sarcomere? | back 24 The distance between the Z lines decreases |
front 25 Kinesin movement along a microtubule is said to be highly ________ meaning that it can move considerable distances along an individual microtubule without falling off. | back 25 processive |
front 26 From what structure do cillia and flagella emerge? | back 26 basal bodies |
front 27 What is the minimum number of kinesin heads in contact with a microtubule at all times? | back 27 1 |
front 28 If you were to fix a fish keratocyte and stain it with fluorescent antibodies for myosin II, where would you see the myosin II? | back 28 in a band where the rear of the lamellipodium joins the rest of the cell |
front 29 What protein is responsible for intraflagellar transport of IFT trains back toward the cell body? | back 29 cytoplasmic dynein |
front 30 Which of the following is a plausible explanation for the fact that the chemical EGTA [ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid; also known as egtazic acid] blocks microtubule disassembly? | back 30 EGTA binds to Ca2+ ions, which are known to induce microtubule depolymerization |
front 31 A single gene can encode a number of related proteins as a result of a process called _______. | back 31 alternative splicing |
front 32 Which polyploidization mechanism is thought to occur most often in plants? | back 32 Two related species mate, forming an organism with the combined chromosomes from both parents. |
front 33 Alcaptonuria is a genetic disease that is characterized by _________. | back 33 urine turning dark upon exposure to the air |
front 34 How might a transposase be responsible for our ability to ward off infectious disease? | back 34 Enzymes involved in antibody gene rearrangement may be derived from a transposase encoded by an ancient DNA transposon. |
front 35 Where is the RNA polymerase II phosphorylated during its activation? | back 35 in the carboxyl-terminal domain (CTD) of the largest RNA polymerase II subunit |
front 36 What causes unequal crossing over? | back 36 A pair of homologous chromosomes aligns imperfectly during meiosis followed by genetic exchange. |
front 37 What is the supposed function of the loops in tRNAs? | back 37 They serve as potential recognition sites for various proteins. |
front 38 Most of the cellular RNA is in what form? | back 38 rRNAs |
front 39 When a gene has been duplicated one or more times, what are the possible things that can happen to the duplicated gene? | back 39 All of these are correct. |
front 40 The enzyme in eukaryotes that is responsible for the synthesis of RNA from a DNA template is called _______. | back 40 DNA-dependent RNA polymerase |
front 41 With what protein does the double-stranded miRNA become associated? The RNA duplex then is disassembled and one of the single strands is incorporated into a RISC complex. | back 41 an Argonaute protein |
front 42 When a gene has been duplicated one or more times, what are the possible things that can happen to the duplicated gene? | back 42 All of these are correct. |
front 43 You incubate eukaryotic cells for 30 minutes in 3H-uridine and then immediately kill the cells and extract the RNA. Where does the radiolabel appear after this experiment? | back 43 in larger RNAs in the cytoplasm |
front 44 The Law of Independent Assortment states that ____________. | back 44 segregation of an allelic pair for one trait has no effect on segregation of alleles for another trait |
front 45 Why does it make sense that cells would be able to recognize dsRNAs as undesirable using a mechanism such as RNAi? | back 45 dsRNAs are not produced by the cell's normal genetic activities. |
front 46 The nucleotide at which transcription is initiated is called _____. | back 46 +1 |
front 47 Which of the following is an RNA nucleoside? | back 47 cytosine and ribose |
front 48 Different versions of a gene are called _________. | back 48 alleles |
front 49 In mammalian cells, radiolabeled methyl groups appear first in what size RNA molecule that is a precursor to rRNA? | back 49 45S RNA |
front 50 The genetic code has 64 codons, while there are only 20 amino acids. Thus, some amino acids are coded for by more than one codon. As a result, the genetic code is said to be ________. | back 50 degenerate |
front 51 The surfaces of the two ribosomal subunits that face one another contain the binding sites for the mRNA and incoming tRNAs and are thus of key importance for the function of the ribosomes. The fact that these surfaces consist largely of RNA supports what proposal? | back 51 the proposal that primordial ribosomes were composed exclusively of RNA |
front 52 What chemical group is attached to the first methionine in a polypeptide chain in prokaryotes? | back 52 a formyl group |
front 53 In a right-handed double helix, if one looks down the central axis of the molecule, _________. | back 53 each strand follows a clockwise path as it moves away from the observer |
front 54 What is the supposed function of the loops in tRNAs? | back 54 They serve as potential recognition sites for various proteins. |
front 55 The reverse reaction of nucleic acid synthesis almost never happens. What prevents it? | back 55 Nucleic acid synthesis is coupled to the highly exergonic pyrophosphate hydrolysis. |
front 56 What provides the energy that drives the polymerization of RNA from a DNA template? | back 56 ribonucleoside triphosphates (NTPs) |
front 57 Mammalian oocytes have recently been shown to produce siRNAs. What are they called? | back 57 endo-siRNAs |
front 58 Which type of enzyme is essential for processes like DNA replication and transcription to prevent excessive supercoiling from developing as the complementary strands of the DNA duplex separate and unwind? | back 58 topoisomerase |
front 59 which of the following is normally associated w the cilia of organisms from protists to mammals? | back 59 a 9+2 pattern |
front 60 a shift in concentration or activity of which type of proteins can cause a shift in the equilibrium between actin monomers and ploymers? | back 60 monomer-sequestering proteins |
front 61 The _______ link is an elastic protein-based linkage that connects tubulin doublets in cilia and flagellae. The resultant bridges play an important role in ciliary and flagellar movement by limiting the extent that adjacent doublets can slide over one another. The resistance to sliding provided by these bridges causes the axoneme to bend. | back 61 nexin |
front 62 What is a major influence in determining the organization and behavior of actin filaments inside cells? | back 62 actin-binding proteins |
front 63 What is the name of the largest protein yet discovered? It extends from the M line in the center of the sarcomere along the myosin filament and past the A band to terminate at the Z line. | back 63 Titin |
front 64 What provides the energy that drives sarcomere contraction? | back 64 ATP |
front 65 In cell biology and with respect to microtubules, intermediate filaments, and microfilaments, the word "dynamic" means ________. | back 65 ever-changing |
front 66 Expression of the Actin assembly-inducing protein (ActA) in previously non-motile strains of bacteria allowed for the _______________ and ___________ characteristic of pathogenic strains. | back 66 formation of actin comet tails, motility |
front 67 How are microtubules thought to affect cell shape in plants? | back 67 Microtubules of the plant cell cortex are thought to affect the movement of cellulose-synthesizing enzymes in the cell membrane, which, in turn, affect cell wall growth and shape. |
front 68 The protein FtsZ acts in the bacterial cell analogously to the ______ cytoskeleton during eukaryotic cytokinesis and is a(n) _________ homolog that is found in nearly all prokaryotic cells. | back 68 actin, tubulin |
front 69 Which of the following does not describe the types of microfilament organization normally seen in cells? | back 69 cylindrical conglomerations |
front 70 Which of the following molecular motors is associated with microfilaments? | back 70 myosins |
front 71 Which of the following molecules is diffusible and serves as an attractant for axons growing within the early embryo? | back 71 netrin |
front 72 For a long time, it was thought that cilia were unimportant or _________, despite their presence on almost all cells. This idea arose because the cilia on most cells are non‐motile, and it was assumed that motility was the key function of cilia. | back 72 vestigial |
front 73 The protein _________ has been implicated in regulating the shape of some bacterial cells; it is expressed in rod-shaped and helical bacteria. It resembles __________in structure. | back 73 MreB, actin |
front 74 Which protein below is often a component of intermediate filaments? | back 74 keratin |
front 75 What chemical below is known to bind to free actin monomers and block their incorporation into the polymer? | back 75 latrunculin |
front 76 Along which structure do membranous vesicles and organelles typically move long distances in an animal cell? | back 76 microtubules |
front 77 The deletion of the creS gene in Caulobacter crescentus results in __________. | back 77 cells that look like straight rods |
front 78 Which of the following words best describes the structure of an actin filament? | back 78 double helix |
front 79 The sperm basal body becomes ______________. | back 79 a centriole during the first mitotic division of the fertilized egg |
front 80 What kind of cells seems to rely mostly on microfilaments for long-distance transport of cytoplasmic vesicles and organelles, probably due to the restricted microtubule distribution in these cells? | back 80 plant cells |
front 81 The protein ParM has been shown to play a role in plasmid segregation during bacterial cell division analogous to the action of ___________ during mitosis and is structurally similar to __________. | back 81 microtubules, actin |
front 82 Which element of the cytoskeleton is found in the cytoplasm and the nucleus? | back 82 intermediate filaments |
front 83 As life was first evolving, what molecule is thought to have performed double duty as the genetic material and performing catalysis of chemical reactions? | back 83 RNA |
front 84 Which of the following is a DNA nucleotide? | back 84 a phosphate group, guanine and deoxyribose |
front 85 What is the significance of the variability of the third nucleotide in a codon? | back 85 The same tRNA can recognize more than one codon. |
front 86 What features set pre-rRNAs apart from other RNA transcripts? | back 86 pseudouridine residues and methylated nucleotides |
front 87 What was the new name of Beadle and Tatum's hypothesis after it was discovered that some enzymes were composed of more than one polypeptide chain? | back 87 the One Gene – One Polypeptide hypothesis |
front 88 While RNA polymerase is a processive enzyme that remains attached to the DNA over long stretches of template, it must be associated _______ enough so that it can move from nucleotide to nucleotide along the template. | back 88 loosely |
front 89 The information encoded in DNA resides in ________. | back 89 the DNA base sequence |
front 90 What word below refers to a pair of homologous chromosomes? | back 90 bivalent |
front 91 Which of the following is not required for protein synthesis? | back 91 anions |
front 92 Transposase is an enzyme that __________. | back 92 catalyzes transposon excision from a donor DNA site and its subsequent insertion at a target DNA site |
front 93 Which of the following is not required for protein synthesis? | back 93 anions |
front 94 The surfaces of the two ribosomal subunits that face one another contain the binding sites for the mRNA and incoming tRNAs and are thus of key importance for the function of the ribosomes. The fact that these surfaces consist largely of RNA supports what proposal? | back 94 the proposal that primordial ribosomes were composed exclusively of RNA |
front 95 DNA sequences in bacteria that on rare occasions moved from one place in the genome to another are called ________. | back 95 transposons |
front 96 You are looking at an electron micrograph of several transcriptional units for rRNA. How can you tell where the transcription initiation site is? | back 96 It is near the shortest nascent transcripts. |
front 97 The greatest variability among codons that specify the same amino acid occurs _________. | back 97 in the third nucleotide of the triplet |
front 98 What molecule is TFIIH known to phosphorylate? | back 98 RNA polymerase II |
front 99 How would you describe the half-lives of rRNAs and tRNAs? | back 99 days or weeks long |
front 100 What kind of DNA is the DNA that codes for rRNA? | back 100 moderately repetitive DNA |
front 101 The building blocks of a nucleotide are ___________. | back 101 a pentose sugar, a phosphate group and a nitrogenous base |
front 102 What is the significance of the variability of the third nucleotide in a codon? | back 102 The same tRNA can recognize more than one codon. |