Bio: Study Set: Lecture 27-32
Base-pair substitutions involving the third base of a codon are unlikely to result in an error in the polypeptide. This is because A) the base-pairing rules are less strict for the third base of codons and anticodons B) substitutions are restricted to introns C) substitutions are corrected before transcription begins D) transcribed errors attract snRNPs, which then stimulate splicing and correction E) a signal-recognition particle corrects coding errors
The correct answer is A
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment? A) one low-density band and one intermediate-density band B) one high-density band and one low-density band C) one intermediate-density band D) one high-density band and one intermediate-density band
The correct answer is A
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules? A) A + G = C + T B) G = T C) A = C D) A + T = C + T E) A = G
The correct answer is A
RNA polymerase binds to a _________ to initiate ____________ A) promoter; transcription B) transcription factor; translation C) primer; transcription D) mRNA; translation
The correct answer is A
Topoisomerases A) break and rejoin DNA to reduce torsional stress B) synthesize DNA C) join Okazaki fragments D) prevent single DNA strands from joining to form a double helix E) synthesize RNA primers
The correct answer is A
Using the DNA strand depicted here as a template, what will be the sequence of the RNA transcript 5' GCGTTAACGTAGGC 3' Promoter ------> 3' CGCAATTGCATCCG 5' A) 5' GCGUUAACGUAGGC 3' B) 5' CGCAAUUGCAUCCG 3' C) 5' CGGAUGCAAUUGCG 3' D) 5' GCCUACGUUAACGC 3'
The correct answer is A
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? A) DNA polymerase can join new nucleotides only to the 3' end of a B) pre-existing strand C) DNA ligase works only in the 3' → 5' direction D) the origins of replication occur only at the 5' end E) helicases and single-strand binding proteins work at the 5' end
The correct answer is A
What would result from the deletion of two bases from a codon in the middle of a gene and one base from the end of the next codon, assuming no stop codons are created? A) all of these would happen B) one amino acid would be deleted; another would be altered C) none of these would happen D) the majority of the protein would be produced correctly E) the protein function might be completely unaffected
The correct answer is A
Which of the following is NOT a component of DNA? A) the pyrimidine uracil B) phosphate groups C) the purine adenine D) five-carbon sugars
The correct answer is A
Which of the following is not true of RNA processing? A) exons are cut out before mRNA leaves the nucleus B) nucleotides may be added at both ends of the RNA C) RNA splicing can be catalyzed by spliceosomes D) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus
The correct answer is A
Which of the following is not true of a codon? A) it extends from one end of a tRNA molecule B) it never codes for more than one amino acid C) it consists of three nucleotides D) it may code for the same amino acid as another codon E) it is the basic unit of the genetic code
The correct answer is A
A gene composed of 600 nucleotides (not counting the promoter or other control elements) would encode a protein of A) 1,800 amino acids B) 200 amino acids C) 1,200 amino acids D) 300 amino acids E) 600 amino acids
The correct answer is B
Considering the structure of a nucleotide, what component is always different when comparing nucleotides in a DNA strand to an RNA strand? A) nitrogenous base B) pentose sugar C) all of these D) phosphate group
The correct answer is B
The anticodon of a particular tRNA molecule is A) catalytic, making the tRNA a ribozyme B) complementary to the corresponding mRNA codon C) changeable, depending on the amino acid that attaches to the tRNA D) complementary to the corresponding triplet in rRNA E) the part of tRNA that bonds to a specific amino acid
The correct answer is B
What does it mean to say that strands in a double helix are antiparallel? A) they each have a sugar-phosphate backbone B) they have opposite directionality, or polarity, in the molecule C) they each have a 5' → 3' directionality D) their primary sequences consist of a sequence of complementary bases
The correct answer is B
Which of the following is typically removed from pre-mRNA during nuclear processing in eukaryotes? A) poly-A tail B) introns C) exons D) upstream leader sequences E) all of these are removed
The correct answer is B
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture? A) Okazaki fragments B) DNA polymerase C) DNA ligase D) primase E) nucleotides
The correct answer is C
DNA attains a secondary structure when hydrogen bonds form between the nitrogenous bases called purines and pyrimidines. What are the complementary base pairs that form in DNA? A) A-G and T-C B) A-C and T-G C) A-T and G-C D) A-U and C-G
The correct answer is C
During replication of a DNA molecule, the daughter strands are not produced in exactly the same manner. One strand, the leading strand, is made toward the replication fork, while the lagging strand is made in fragments in the opposite direction. This difference in the synthesis of the two strands is the result of which of the following? A) The cell does not contain enough nucleotides to make two complete strands B) The lagging strand is the result of DNA breakage due to UV light C) The two template strands are antiparallel, and DNA polymerase makes DNA only in the 5' to 3' direction D) DNA polymerase is not efficient enough to make two "good" strands of DNA
The correct answer is C
For a protein to fold correctly, it must bind to other proteins called A) histones B) enhancers C) chaperones D) promoters
The correct answer is C
Hershey and Chase used radioactive phosphorus and sulfur to A) kill the bacteriophage after a single round of replication B) kill the bacteria after a single round of replication C) label DNA and protein differentially D) label DNA and protein uniformly
The correct answer is C
If a segment of DNA is 5'-CATTAC-3', the complementary DNA strand is: A) 5'-CATTAC-5' B) 5'-GTAATG-3' C) 3'-GTAATG-5' D) 3'-CATTAC-5' E) 5'-CATTAC-3'
The correct answer is C
If you could engineer an activity into DNA polymerase to allow both strands to follow the replication fork, what would this additional activity be? A) the ability to proofread in the 5'→3' direction B) the ability to synthesize DNA without using a template C) the ability to synthesize in the 3'→5' direction D) the ability to begin DNA synthesis without a primer
The correct answer is C
In his work with pneumonia-causing bacteria and mice, Griffith found that A) the polysaccharide coat of bacteria caused pneumonia B) bacteriophages injected DNA into bacteria C) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic D) the protein coat from pathogenic cells was able to transform nonpathogenic cells E) heat-killed pathogenic cells caused pneumonia
The correct answer is C
Suppose you mix the following components of protein synthesis in a test tube: amino acids from a rabbit; ribosomes from a dog; tRNAs from a mouse; mRNA from a chimpanzee; and necessary enzymes plus an energy source from a giraffe. If protein synthesis occurs, which animal's protein will be made? A) mouse B) dog C) chimpanzee D) giraffe E) rabbit
The correct answer is C
Synthesis of a new DNA strand usually begins with A) a thymine dimer B) an Okazaki fragment C) an RNA primer D) a DNA primer E) DNA ligase
The correct answer is C
The statement "DNA replicates by a semiconservative mechanism" means that: A) the two strands of a double helix have identical base sequences B) some portions of a single DNA strand are old, and other portions are newly synthesized C) each double helix consists of one old and one newly synthesized strand D) first one DNA strand is copied, and then the other strand is copied E) only one strand of DNA is copied
The correct answer is C
The two complementary strands of the DNA double helix are held to one another by A) covalent bonds between deoxyribose molecules B) ionic bonds between phosphate groups C) hydrogen bonds between nucleotide bases D) ionic bonds between deoxyribose molecules E) covalent bonds between nucleotide bases
The correct answer is C
What are the four nitrogenous bases found in RNA? A) uracil, guanine, cytosine, thymine (U, G, C, T) B) adenine, guanine, cytosine, thymine (A, G, C, T) C) adenine, uracil, guanine, cytosine (A, U, G, C) D) alanine, threonine, glycine, cysteine (A, T, G, C)
The correct answer is C
Which of the following is not a property of DNA polymerase? A) it requires a primer to work B) its exonuclease activity is involved in proofreading C) it is associated with a sliding clamp only on the leading strand D) it catalyzes the addition of nucleotides only in the 5'→ 3' direction
The correct answer is C
Why did researchers suspect that DNA does not code for proteins directly? A) in prokaryotes, DNA and proteins are never found together B) when DNA was damaged by ultraviolet radiation or other sources of energy, the proteins in the cell did not change C) in eukaryotes, DNA is found in the nucleus, but proteins are produced outside the nucleus D) there are several distinct types of RNA, of which only one functions as messenger RNA
The correct answer is C
A ribosome binds to the following mRNA at the site indicated by the dark box. What are the first three amino acids that will be incorporated into the resulting polypeptide? (Hint - you don't actually need the genetic code table to figure this one out). 5' aaaaaaa GCCGGAAUGCUGCUGGC A) alanine/aspartic acid/alanine B) methionine/threonine/cysteine C) alanine/glycine/methionine D) methionine/leucine/leucine
The correct answer is D
Chromatin fibers include A) RNA and phospholipids B) DNA and structural polysaccharides C) triacylglycerol and steroids D) DNA and protein E) protein and carbohydrates
The correct answer is D
In a nucleosome, the DNA is wrapped around A) a thymine dimer B) ribosomes C) polymerase molecules D) histones
The correct answer is D
The RNA splicing process A) occurs in all cells and organisms B) joins introns together C) joins exons to introns D) can produce multiple mRNAs from the same transcript
The correct answer is D
The ___ is the site where the translation process takes place A) mitochondria B) nucleus C) lysosome D) ribosome E) plasma membrane
The correct answer is D
The majority of gene expression regulation occurs by exerting control over the production of mRNA. Where is most gene regulation taking place? A) at the level of post-transcriptional processing B) at the level of post-translational modification C) at the level of translation D) at the level of transcription
The correct answer is D
The ribozyme that forms peptide bonds is called peptidyl transferase because it transfers...(this one is tricky, pay attention!) A) the peptide from the ribosome to a charged tRNA B) the peptide from one amino acid to another C) a new amino acid from a tRNA to the growing peptide D) the growing peptide from a tRNA to the next amino acid
The correct answer is D
The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage? A) telomerase, helicase, single-strand binding protein B)DNA ligase, replication fork proteins, adenylyl cyclase C) telomerase, primase, DNA polymerase D) nuclease, DNA polymerase, DNA ligase
The correct answer is D
What is the central dogma of genetics (molecular biology)? A) DNA is the genetic material B) one gene encodes only one polypeptide C) information passes from DNA directly to protein D) information passes from DNA to RNA to protein
The correct answer is D
Why did researchers initially believe the genetic material was protein? A) proteins are found only in the nucleus, but DNA is found in many areas of the cell B) all of the above C) proteins are much larger molecules than DNA D) proteins are more biochemically complex (have more possibility for diverse sequences) than DNA
The correct answer is D
RNA grows in the ____ direction, as RNA polymerase moves along the template DNA strand in the _____ direction. A) 5'→5'; 3'→3' B) 5'→3'; 5'→3' C) 3'→5'; 3'→5' D) 3'→5'; 5"→3' E) 5'→3'; 3'→5' F) 3'→3'; 5'→5'
The correct answer is E
Select the steps of an elongation cycle during protein synthesis from the following list, and place them in the proper sequence: Peptide bond formation Binding of the small ribosomal subunit to the 5' end of the mRNA Binding of aminoacyl tRNA to the A site Translocation of the ribosome A) 2→1→3→4 B) 1→3→2→4 C) 3→1→3→2 D) 4→2→1→3 E) 2→3→1→4
The correct answer is E
Transcription is the process by which_______ is/are synthesized: A) protein B) mRNA, tRNA, rRNA and protein C) mRNA and tRNA D)mRNA only E) mRNA, tRNA and rRNA
The correct answer is E
Which of the following mutations would be most likely to have a harmful effect on an organism? A) a single nucleotide deletion in the middle of an intron B) a base-pair substitution C) a deletion of three nucleotides near the middle of the gene D) a single nucleotide deletion near the end of the coding sequence E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence
The correct answer is E