Q&A Hero

Q: rRNA strands exhibit which of the following: a. instrastrand sequence complementarity b. highly folded patterns including many stem-loop structures c. an anticodon loop d. both a and b e. a, b and c

Q: The major interactions that fold components of the secondary structure of tRNA together and bend the cloverleaf into a stable L-shaped tertiary form are: a. hydrophobic interactions. b. base-pairing interactions. c. ionic interactions. d. electrostatic interactions. e. both a and b.

Q: All are secondary structure components of tRNA EXCEPT:a. acceptor stem.b. D loop.c. Anticodon loop.d. T™C loop.e. All are true.

Q: Individual amino acids are attached to their corresponding tRNAs: a. through an ester linkage to the 3'-OH in the acceptor stem. b. through an amide linkage to the anticodon loop. c. through an amide linkage to the adenine ring at the 3'end of the tRNA. d. through a phosphoester linkage to the 5' end of the tRNA. e. None of the above.

Q: Histones are rich in the amino acids ____, and interact with DNA via ____. a. alanine and glycine; covalent bonds b. glutamic acid and aspartic acid; hydrogen bonds c. glutamic acid and aspartic acid; ionic bonds d. lysine and arginine; hydrogen bonds e. lysine and arginine; ionic bonds

Q: All are properties of nucleosomes EXCEPT: a. protein spools neatly wrapped with DNA. b. fundamental structural unit in chromatin. c. protein spools made up of pairs of histones H2A, H2B, H3 and H4 octameric aggregates. d. DNA binds histones by ionic bonds of positively charged amino acids and the negative charged phosphate groups. e. all are true.

Q: DNA sequences that are inverted repeats, or ____, have the potential to form a ____ structure known as a ____ if the normal ____ base pairing is replaced by ____ pairing. a. probes; secondary; cruciform; interstrand; intrastrand b. palindromes; tertiary; cruciform; interstrand; intrastrand c. cruciforms; secondary; palindrome; intrastrand; interstrand d. palindromes; tertiary; cruciform; intrastrand; interstrand e. none are true.

Q: All are characteristics of DNA gyrase in E.coliEXCEPT: a. It hydrolyzes ATP during its reaction mechanism. b. It cuts both strands of a dsDNA. c. It works to induce negative supercoiling in DNA. d. It is classified as a topoisomerase. e. All are true.

Q: The function of DNA topoisomerases is: a. packaging DNA into nucleosomes. b. forming cruciform DNA. c. unwinding G:C rich areas in DNA. d. breaking one or more strands of DNA, winding them tighter or looser, and rejoining the ends. e. promoting DNA hybridization.

Q: All are true for linking number EXCEPT: a. It is a basic parameter characterizing supercoiled DNA. b. L = T + W. c. It is the number of times that two strands are intertwined providing both strands remain covalently intact. d. L = 40 in a relaxed circular DNA duplex of 400 bp. e. All are true.

Q: DNA ____ is analogous to twisting or untwisting a two stranded rope so that it is torsionally stressed. a. buoyant density b. hairpin turn c. cloverleaf d. supercoiling e. all of the above

Q: Naturally occurring, self-replicating, extra-chromosomal DNA molecules found in bacteria that carry genes specifying novel metabolic capacity advantageous to the bacterium are called: a. probes. b. cruciform. c. toroidal DNA. d. plasmids. e. all of the above.

Q: Nucleic acid hybridization is a commonly employed procedure in molecular biology to investigate all EXCEPT: a. evolutionary relationships. b. specific genes against a vast background. c. specific probe based isolation of genes. d. quantify gene expression. e. all are true.

Q: B-DNA is characterized by which of the following? a. 12 base pairs per helix turn b. helix axis runs through the minor groove c. a wide major groove an narrow minor groove d. right-handed helix e. both C and D are correct

Q: Which of the following enzymes introduces negative supercoils into DNA? a. DNA polymerase b. DNA gyrase c. DNA ligase d. primase e. DNA photolyase

Q: ssDNA will renature requiring ____ of the DNA strands into a dsDNA and this is called ____ which occurs best if the temperature is ____ Tmbut warm enough to promote diffusion of the DNA molecules. a. hydrolysis; reannealing; below b. reassociation; reannealing; below c. reassociation; melting; above d. complementing; solidifying; below e. none are true

Q: Urea and formamide are agents that denature dsDNA by a. intercalating between base pairs and disrupting van der Waals interactions. b. forming ionic bonds with the backbone phosphates. c. competing effectively with the H-bonding between the base pairs. d. changing the pH to cause hydrolysis. e. none are true

Q: The higher the ____ content of a DNA, the ____ the melting temperature, and the ____ the ionic strength, the ____ the melting temperature. a. G:C; higher; higher; lower b. G:C; lower; higher; lower c. G:C; higher; lower; lower d. A:T; higher; higher; lower e. A:T; lower; lower; higher

Q: The hyperchromic shift that occurs when dsDNA is ____ is a(n) ____ in absorption at ____ nm. a. methylated; increase; 220 b. methylated; decrease; 260 c. denatured; decrease; 260 d. denatured; increase; 260 e. melted; decrease; 280

Q: DNA intercalating agents include all of the following EXCEPT: a. ethidium bromide. b. actinomycin D. c. acridine orange. d. streptomycin. e. all are true.

Q: Double helical DNA:RNA hybrids and double-stranded regions of RNA chains often assume an: a. A-like conformation. b. B-like conformation. c. Z-like conformation. d. all of the above. e. none of the above.

Q: All of the following are characteristics for in vitroDNA synthesis EXCEPT:a. DNA polymerase adds nucleotides in a 5'-3' direction.b. The primer strand of DNA determines the nucleotides added.c. Correct hydrogen bonding is the primary check of the newly synthesized DNA.d. A primer strand must contain a free 3'-OH.e. DNA polymerase copies the complementary strand of DNA.

Q: DNA double helix structure is stabilized by all of the following EXCEPT: a. the sugar-phosphate backbones are oriented in opposite directions. b. the glycosidic bonds holding paired bases are directly across the helix from one another. c. cations such as Mg2+ bind to the anionic phosphates. d. bases stack together through hydrophobic interactions and van der Waals forces. e. appropriate base pairing builds a polymer whose external dimensions are uniform.

Q: All are true for DNA polymerase EXCEPT: a. requires a primer with a free 5'-OH end, but the 3'-end may be phosphorylated. b. copies the sequence of nucleotides of one strand to form a new second strand. c. copies the sequence of nucleotides of one strand in a complementary fashion. d. generates dsDNA from ssDNA e. synthesizes new strands by adding successive nucleotides in the 5'ï‚®3' direction.

Q: How is a fluorescent tag that is unique for each nucleotide incorporated into the newly synthesized DNA using the chain termination protocol for DNA sequencing? a. Each of the ddNTPs is labeled with a specific fluorophore b. The primer strand is labeled with a specific fluorophore c. The template strand is labeled prior to the experiment with complimentary fluorophores d. The 5'-end is labeled with a fluorophore. e. All dNTPs are labeled with a fluorophore

Q: Which of the following statements correctly describes the process of DNA sequencing by chain termination? a. the enzyme DNA polymerase is used to form a primer that binds to the template DNA b. in order to effectively sequence the DNA, the dideoxynucleotides must be present at a higher concentration than the deoxynucleotides c. the use of 4 unique fluorescent labels attached to the dideoxynucleotides allows for a single reaction to be run d. the dideoxynucleotides lack a 5'-OH and therefore can not serve as acceptors in nucleotide addition e. both B and C are correct

Q: Which of the following explains why it is often easier to sequence a gene rather than sequence the corresponding protein? a. DNA sequencing can be performed on picogram quantities of DNA b. DNA is composed of only 4 different monomers while proteins are composed of 20 different monomers c. restriction endonucleases can be used to cut DNA at specific sequences to generate DNA fragments that can easily be sequenced d. all of the above e. both B and C are correct

Q: All are necessary for restriction endonuclease mapping of DNA molecules EXCEPT:a. Determining the 5'- and or 3'-ends of the molecule.b. Electrophoresis of fragments.c. Hydrolysis with two or more endonucleases.d. Knowing where each endonuclease hydrolyzes.e. All are true.

Q: Which of the following statements correctly identifies a type II restriction endonuclease? a. They work on both DNA and RNA. b. They recognize a palindromic sequence and cut just before the palindromic sequence. c. The result of this endonuclease is blunt ends. d. They degrade DNA by subsequently removing bases from each end. e. They cut DNA only at sites in specific nucleotide sequences with a two-fold axis of symmetry.

Q: All are true for enzymes that cleave nucleic acids EXCEPT: a. They are of the lyase class of enzymes. b. They are called nucleases. c. They belong to the sub-class of phosphodiesterases. d. They are found in all cells for "house keeping", and secreted by the pancreas for digestion. e. They are found in fungi and snake venoms

Q: RNA is ____ stable to alkaline hydrolysis than DNA because RNA's vicinal ____ group makes the 3'-phosphodiester bond susceptible to ____ cleavage. a. less; 3'-OH; nucleophilic b. less; 2'-OH; nucleophilic c. more; 2'-OH; electrophilic d. more; 2'-OH; nucleophilic e. more; 3'-OH; electrophilic

Q: ____ are important in the processing of eukaryotic gene transcripts into mature messenger RNAs for export from the nucleus into cytoplasm. a. snRNAs as snRNPs b. tRNAs c. rRNAs d. siRNAs e. stRNAs

Q: Which of the following correctly describes tRNA molecules?a. each amino acid in proteins has at least three unique tRNA species dedicated to chauffeuring its delivery to ribosomes for insertion into growing polypeptides.b. they are small molecules containing 73 or 74 bases.c. they often contain bases such as inosine or pseudouridined. the 5- end of the molecule is the site of attachment for the amino acide. none of the above is correct

Q: 30S rRNA is a designation of the ____ of the RNA molecule. a. number of sugars b. sedimentation coefficient c. splicing coefficient d. sequence repeats e. splicing number

Q: ____ are attached to hnRNAs and mRNAs after transcription has been completed and is essential for efficient translation and stability of the mRNAs. a. exons b. entrons c. poly(A) tails d. poly(U) tails e. All are true

Q: Eukaryotic mRNAs are synthesized in the nucleus, are called ____, and contain noncoding regions called ____ because they intervene between coding regions called ____. a. poly A RNAs; noncodons; codons b. poly A RNAs; intervening sequences; codons c. heterogeneous nuclear RNAs; intervening sequences (introns); codons d. heterogeneous nuclear RNAs; intervening sequences (introns); exons e. none of the above.

Q: Prokaryotic chromosomes are typically ____, while eukaryotic chromosomes are ____ a. circular; linear and richly protein-associated b. circular and richly protein-associated; linear c. linear and richly protein-associated; circular d. linear; circular and richly protein-associated e. none are true.

Q: In eukaryotic cells, a class of ____- and ____-rich proteins called ____ interact ionically with the anionic phosphate groups in the DNA backbone to form ____. a. lysine; leucine; prions; ribosomes b. arginine; lysine; histones; nucleosomes c. arginine; alanine; histones; nucleosomes d. arginine; lysine; prions; ribosomes e. none are true.

Q: In eukaryotic cells, DNA is found principally in the nucleus, but it also occurs in ____ and in ____. a. ribosomes; mitochondria b. mitochondria; chloroplasts c. chloroplasts; peroxisomes d. peroxisomes; vacuoles e. vacuoles; mitochondria

Q: What is the nucleotide sequence of the DNA strand that is complementary to 5'-ATCGCAACTGTCACTA-3'? a. 5'-TAGCGTTGACAGTGAT-3' b. 5'-UAGUGACAGUUGCGAU-3' c. 5'-TAGCGTTGACAGTGAT-3' d. 5'-TAGTGACAGTTGCGAT-3' e. 5'-ATCACTGTCAACGCTA-3'

Q: All of the following are important characteristics of DNA EXCEPT: a. a 1:1 ratio between pyrimidine residues and purine residues. b. adenine base pairs with uracil. c. hydrogen bonding between base pairs. d. information contained in the sequence of one strand conserved in the sequence of other strand. e. information is accessed through transcription of the information into RNA.

Q: The convention in all notations of nucleic acid structure is to read the polynucleotide chain from the ____ of the polymer to the ____. a. poly U head; poly A tail b. 3'-end; 5'-tail c. 5'-end; 3'-end d. poly-p head; 5'-end e. none are true

Q: In a sample of double-stranded DNA containing 32% cytosine, the percentage of adenine would be: a. 32% b. 68% c. 18% d. 0% e. insufficient information to answer question

Q: In a double-stranded nucleic acid, guanine typically base-pairs with: a. adenosine. b. uracil. c. inosine. d. thymine. e. cytosine.

Q: Which of the following statements regarding the structure of DNA is correct? a. the two strands are parallel. b. the two strands are held together by intrachain hydrogen bonds. c. the two strands have complementary base pairing. d. the hydrogen bonding that holds the helix together is always between two purines or between two pyrimidines. e. the ratio of adenine to guanine is the same in all organisms.

Q: In phosphoryl group transfer reactions, the ____ of the nucleotide serves as an information symbol, channeling the nucleotide to appropriate metabolic activities. a. sugar b. diphosphate anhydride c. sugar-phosphate ester d. base e. none are true

Q: Nucleotide triphosphates and nucleotide diphosphates often form stablecomplexes with: a. Na+ b. Fe+3 c. K+ d. Mg+2 e. None of the above.

Q: All of the following are examples of nucleotide functions EXCEPT: a. CTP in phospholipid synthesis. b. UTP in complex carbohydrate synthesis. c. ATP in energy for the cell. d. GTP in protein synthesis. e. TTP in phosphoryl group transfers.

Q: Which molecule contains an phosphoanhydride bond? a. DNA b. AMP c. UDP d. RNA e. cAMP

Q: cAMP and cGMP are ____ with phosphate esterified as a cyclic ____ and are important as ____ of cellular metabolism. a. nucleotides; phosphodiester; inhibitors b. nucleotides; phosphomonoesters, regulators c. nucleotides; phosphodiesters, regulators d. nucleosides; phosphomonoesters, stimulators e. all of the above

Q: The net charge on nucleotide monophosphates is:a. +1b. 0c. -­1d. -2e. -3

Q: Nucleosides are relatively stable to ____ hydrolysis, and pyrimidine nucleotides are stable to ____ hydrolysis, but purine nucleotides are unstable to ____ hydrolysis. a. base; acid; acid b. base; base; acid c. acid; base; base d. acid; acid; base e. none are true

Q: Nucleotides have a nitrogenous base linked to a sugar by a:a. -anhydride bond.b. -ester bond.c. -N-amide bond.d. -N-acetal (glycosidic) bond.e. -N-hemiacetal bond.

Q: Which of the following properties describe both purines and pyrimidines? a. they are aromatic b. they are composed of 6-membered rings c. they exhibit strong absorption of UV light d. they always contain a carbonyl group e. both A and C are correct

Q: All are characteristics of pyrimidines EXCEPT: a. six membered ring. b. heterocyclic. c. conjugated. d. fused five membered rings. e. two nitrogens separated by a carbonyl.

Q: All are important functional groups participating in H-bond formation EXCEPT: a. amino group of the cytosine, adenine and guanine. b. the ring nitrogens at position 3 of pyrimidines and 1 of purines. c. the electronegative oxygen atoms. d. the electron density in the double bonds of the bases. e. the carbonyl group at position 4 of uracil and thymine, position 2 of cytosine, and position 6 of guanine.

Q: ____ is the most oxidized state for a purine derivative and is ____ found in nucleic acids. a. Guanine; always b. Adenine; always c. Hypoxanthine; never d. Xanthine; always e. Uric acid; never

Q: Which is a six-membered heterocyclic aromatic ring? a. pyrimidine b. purine c. anose d. sugar portion of DNA e. ribonucleotide

Q: Complete hydrolysis of nucleic acids liberates all of the following EXCEPT: a. 2-deoxyribose from DNA. b. nitrogenous bases. c. amino acids. d. phosphoric acid. e. ribose from RNA.

Q: Which of the following restriction sites would provide staggered 3-ends? The restriction site in each sequence is shown with an arrow.a. 5- -TTCGAA-3-b. 5- -GTTAAC-3-c. 5- -CCCGGG-3-d. 5- -CTGCAG-3-e. none of the above

Q: Inosine, one of the common alternative bases found in RNA, is shown below. How would inosine form hydrogen bonds in a double helical section of RNA? a. 1 H-bond donor group, 0 H-bond acceptor groups b. 0 H-bond donor groups, 1 H-bond acceptor group c. 1 H-bond donor group, 1 H-bond acceptor group d. 2 H-bond donor groups, 1 H-bond acceptor group e. 1 H-bond donor group, 2 H-bond acceptor groups

Q: If a restriction site of 6 bases starts with 5- -TGG, what are the last three bases in the sequence?a. 5- -ACC-3-b. 5- -GGT-3-c. 5- -CCA-3-d. 5- -TGG-3-e. none of the above

Q: In a typical Na+,K+-ATPase, _____ sodium ions are moved from the _____ of the cell while _____ potassium ions are moved from the _____ of the cell a. 2; inside to outside; 3; outside to inside b. 3; inside to outside; 2; outside to inside c. 2; outside to inside; 3; inside to outside d. 3; outside to inside; 2; inside to outside e. none of the above

Q: The transport of glutamine across a membrane was measured, and the results obtained are presented in the following table. What type of transport does Gln exhibit? a. primary active transport b. secondary active transport c. passive diffusion d. facilitated diffusion e. cannot determine from the given data

Q: Indole (the structure shown below) will cross a membrane about 1000 times faster than tryptophan. Which of the following is the most likely explanation for this phenomenon? a. there is a specific secondary active transporter for indole while tryptophan moves by facilitated diffusion b. indole can easily move through a lipid bilayer by simple diffusion while tryptophan movement is slowed by the presence of ionized functional groups c. both tryptophan and indole use the same transporter protein which has a much higer affinity for indole than for tryptophan d. since indole is not normally present in biological systems, it is not bound to proteins that would prevent transport in the manner that tryptophan is e. none of the above

Q: Secondary active transport across a membrane refers to a. Movement of a molecule across a membrane and against its concentration gradient powered by an ion gradient that is created by a different transporter b. Movement of a molecule across a membrane and against its concentration gradient through a transporter that is directly powered by ATP hydrolysis c. Movement of a molecule across a membrane powered by its own concentration gradient d. Movement of a molecule across a membrane through a transporter that has an alpha-helical secondary structure. e. none of the above

Q: Mobile carriers and pores (or channels) can be distinguished based on the ____ dependence of mobile carrier transport. a. pH b. ionic strength c. proton gradient d. temperature e. none of the above

Q: Ionopore antibiotics are small-molecule toxins produced by microorganisms to facilitate ion transport across membranes and include all EXCEPT: a. actinomycin. b. valinomycin. c. nonactin. d. monensin. e. gramicidin A.

Q: Gap junctions allow cells to communicate metabolically and are sensitive to: a. pH changes. b. membrane potentials. c. intracellular calcium levels. d. hormonal signals. e. all of the above.

Q: Melittin is a 26-residue peptide in honeybee venom that:a. has ionophore antibiotic properties.b. is a phospholipase that attacks red blood cells causing hemolysis.c. forms -helical aggregates with amphipathic character in membranes.d. is toxic to Na+, K+-ATPase.e. discharges mitochondrial proton gradients and ATP synthesis.

Q: Pore-forming toxins solve the problem of a need to provide hydrogen-bonding partners for the polypeptide background N-­H and C=O groups in the bilayer that lacks hydrogen-bond donors and acceptors by utilizing extensive:a. salt bridge formation.b. disulfide bond formation.c. -turns.d. -helices and -sheets.e. none of the above.

Q: The System A for alanine transport into liver is a(n) ____ system that can be activated by ____ and ____. a. Na+-symport; substrate (alanine); hormones b. K+-symport; substrate (alanine); hormones c. H+-antiport; pH change; alanine d. ATP-antiport; alanine; pH change e. None are true

Q: Bacteriorhodopsin affects a light driven ____ proton transport that results in a proton gradient sufficient to drive ____. a. inward; Na+-import b. outward; ATP synthesis c. inward; K+-export d. outward; light emission e. none are true

Q: Multiple Drug Resistant (MDR)-ATPase is a ____ repeat protein that uses ATP hydrolysis to actively transport a wide variety of drugs ____ the cell. a. multiple; into b. multiple; out of c. tandem; into d. tandem; out of e. triple; into

Q: Yeast -factor ATPase and MDR ATPase are two members of a superfamily of transport proteins that actively transport:a. H+ to dissolve bone mineral.b. Ca2+ into the sarcoplasm.c. a broad group of diverse organic molecules across membranes.d. Mg2+ against a concentration gradient.e. none of the above.

Q: H+-transporting ATPases found in ____ break down bone during normal bone remodeling are of the ____ type of ATPases. a. osteoclasts; vacuolar (V-) b. osteoclast; H+, K+-ATPase c. osteoblast; H+, K+-ATPase d. osteoblast; vacuolar (V-) e. osteoclast; Na+, K+-ATPase

Q: All are characteristic of the gastric proton pump EXCEPT: a. Gastric proton pump requires high levels of dietary K+ to create a K+ gradient. b. Gastric proton pump is a H+, K+-ATPase. c. Gastric proton pump maintains a pH gradient of about 6.6 across the mucosal cell membrane. d. Gastric proton pump is electroneutral. e. Gastric proton pump produces a net influx of HCl into the stomach.

Q: The Ca2+-ATPase structure is like many of the other active transport proteins in that it has all of the components EXCEPT:a. transmembrane domain of ten -helical segments.b. a large cytoplasmic domain with nucleotide binding domain.c. a phosphorylation domain.d. an actuator domain.e. all are true.

Q: Nearly all of the calcium ions in muscle are sequestered inside vesicles called: a. mitochondria. b. sarcoplasmic reticulum. c. endoplasmic reticulum. d. Golgi. e. secretory vesicles.

Q: Muscle Ca2+-ATPase resembles Na+, K+-ATPase in many ways EXCEPT:a. Both have -subunits of similar size.b. Both form covalent E-P intermediates during ATP hydrolysis.c. Both have similar mechanisms of ATP hydrolysis.d. Both have similar ion transport mechanisms.e. Both have residence on the sarcoplasmic reticulum.