Gene to Protein
What are the coding segments of a stretch of eukaryotic DNA called? Answers: replicons exons codons transposons introns
Selected Answer: exons
What is the sequence of a peptide based on the following mRNA sequence? 5' . . . UUUUCUUAUUGUCUU 3' Answers: leu-pro-asp-lys-gly leu-cys-tyr-ser-phe phe-ser-tyr-cys-leu cyc-phe-tyr-cys-leu cyc-phe-tyr-cys-leu
Selected Answer: phe-ser-tyr-cys-leu
Which of the following is true for both prokaryotic and eukaryotic gene expression? Answers: mRNA is synthesized in the 3' → 5' direction. Translation of mRNA can begin before transcription is complete RNA polymerase binds to the promoter region to begin transcription After transcription, a 3' poly-A tail and a 5' cap are added to mRNA The mRNA transcript is the exact complement of the gene from which it was copied
Selected Answer: RNA polymerase binds to the promoter region to begin transcription
If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides? Answers: 4 2 12 3 1
Selected Answer: 2
Which of the following help(s) to stabilize mRNA by inhibiting its degradation? Answers: 5' cap and poly (A) tail RNA polymerase TATA box introns spliceosomes
Selected Answer: 5' cap and poly (A) tail
Using the figure, identify a 5' → 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys Answers: 5'-AAAACCTTT-3' 5'-CTTCGGGAA-3' 5'-AAACCCUUU-3' 5'-GAACCCCTT-3' 5'-UUUGGGAAA-3'
Selected Answer: 5'-CTTCGGGAA-3'
Which of the following is not true of RNA processing? Answers: Ribozymes may function in RNA splicing RNA splicing can be catalyzed by spliceosomes A primary transcript is often much longer than the final RNA molecule that leaves the nucleus Nucleotides may be added at both ends of the RNA. Exons are cut out before mRNA leaves the nucleus
Selected Answer: Exons are cut out before mRNA leaves the nucleus
The "universal" genetic code is now known to have exceptions. Evidence for this could be found if which of the following is true? Answers: If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites If several codons are found to translate to the same amino acid, such as serine If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA. If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide. If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).
Selected Answer: If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).
Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because Answers: tRNA, rRNA and others are not transcribed only one mRNA molecule can be transcribed from a single gene, lowering the potential rate of gene expression. RNA acts as an expendable copy of the genetic material RNA is much more stable than DNA. mRNA molecules are subject to mutation but DNA is not RNA is much more stable than DNA.
Selected Answer: RNA acts as an expendable copy of the genetic material RNA is much more stable than DNA.
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? Answers: primase RNA polymerase I RNA polymerase III ligase RNA polymerase II
Selected Answer: RNA polymerase II
As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs? Answers: The tRNA that was in the A site departs from the ribosome via a tunnel The tRNA that was in the P site moves into the A site. The tRNA that was in the A site moves into the P site. The polypeptide enters the E site The tRNA that was in the A site moves to the E site and is released
Selected Answer: The tRNA that was in the A site moves into the P site.
Of the following, which is the most current description of a gene? Answers: a unit of heredity that causes formation of a phenotypic characteristic a DNA—RNA sequence combination that results in an enzymatic product a DNA sequence that is expressed to form a functional product: either RNA or polypeptide a discrete unit of hereditary information that consists of a sequence of amino acids a DNA subunit that codes for a single complete protein
Selected Answer: a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation? Answers: an accumulation of A and B and no production of C an accumulation of A and no production of B and C an accumulation of B and no production of A and C an accumulation of C and no production of A and B an accumulation of B and C and no production of A
Selected Answer: an accumulation of A and no production of B and C
Alternative RNA splicing Answers: can allow the production of similar proteins from different RNAs increases the rate of transcription is a mechanism for increasing the rate of transcription. is due to the presence or absence of particular snRNPs. can allow the production of proteins of different sizes from a single mRNA
Selected Answer: can allow the production of proteins of different sizes from a single mRNA
What are polyribosomes? Answers: groups of ribosomes reading a single mRNA simultaneously ribosomes containing more than two subunits multiple copies of ribosomes associated with giant chromosomes aggregations of vesicles containing ribosomal RNA ribosomes associated with more than one tRNA
Selected Answer: groups of ribosomes reading a single mRNA simultaneously
If A, B, and C are all required for growth, a strain that is mutant for the gene encoding enzyme A would be able to grow on which of the following media? Answers: minimal medium supplemented with nutrient "B" only minimal medium minimal medium supplemented with nutrient "A" only minimal medium supplemented with nutrient "C" only minimal medium supplemented with nutrients "A" and "C"
Selected Answer: minimal medium supplemented with nutrient "B" only
A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. Which enzyme causes a covalent bond to attach lysine to the polypeptide? Answers: RNA polymerase lysine synthetase ligase peptidyl transferase ATPase
Selected Answer: peptidyl transferase
Transcription in eukaryotes requires which of the following in addition to RNA polymerase? Answers: ribosomes and tRNA the protein product of the promoter start and stop codons several transcription factors (TFs) aminoacyl synthetase
Selected Answer: several transcription factors (TFs)
Which of the following is not true of a codon? Answers: It is the basic unit of the genetic code It consists of three nucleotides It never codes for more than one amino acid It may code for the same amino acid as another codon It extends from one end of a tRNA molecule.
Selected Answer: It extends from one end of a tRNA molecule.
How many genes are necessary to synthesize this pathway? Answers: 0 1 3 2 It cannot be determined from the pathway
Selected Answer: 2
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is Answers: either UCA or TCA, depending on wobble in the first base. 3' UGA 5' 5' TCA 3'. 3'ACU 5' 3' UCA 5'.
Selected Answer: 3' UCA 5'.
A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide? Answers: 5' TTT-CCC-AAA-GGG-TTT-CCC 3' UUU-CCC-AAA-GGG-UUU-CCC 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG
Selected Answer: 5' TTT-CCC-AAA-GGG-TTT-CCC
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which might this illustrate? Answers: The sequence does not mutate. The sequence is found in many but not all promoters. The sequence evolves very rapidly The sequence is transcribed at the start of every gene. Any mutation in the sequence is selected against.
Selected Answer: Any mutation in the sequence is selected against.
Which component is not directly involved in translation? Answers: ribosomes GTP tRNA DNA mRNA
Selected Answer: DNA
Why might a point mutation in DNA make a difference in the level of protein's activity? Answers: It might exchange one serine codon for a different serine codon. It might result in a chromosomal translocation. It might substitute an amino acid in the active site It might exchange one stop codon for another stop codon. It might substitute the N terminus of the polypeptide for the C terminus.
Selected Answer: It might substitute an amino acid in the active site
Each of the following options is a modification of the sentence THECATATETHERAT. Which of the following is analogous to a single substitution mutation? Answers: THERATATETHECAT THETACATETHERAT CATATETHERAT THECATARETHERAT THECATATTHERAT
Selected Answer: THECATARETHERAT
Each of the following options is a modification of the sentence THECATATETHERAT. Which of the following is analogous to a frameshift mutation? Answers: CATATETHERAT THECATARETHERAT THERATATETHECAT THECATATTHERAT THETACATETHERAT
Selected Answer: THECATATTHERAT
An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result? Answers: The anticodon will not bind with the mRNA codon. The amino acid methionine will not bind. The nearby stem end will pair improperly. tRNA will not form a cloverleaf. The aminoacylsynthetase will not be formed
Selected Answer: The amino acid methionine will not bind.
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly(A) tail. Which of the following would you expect him to find? Answers: The molecule attaches to a ribosome and is translated, but more slowly The mRNA could not exit the nucleus to be translated The cell recognizes the absence of the tail and polyadenylates the mRNA The molecule is digested by restriction enzymes in the nucleus The molecule is digested by exonucleases since it is no longer protected at the 5' end
Selected Answer: The molecule is digested by exonucleases since it is no longer protected at the 5' end
As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs? Answers: The tRNA that was in the A site moves into the P site. The tRNA that was in the P site moves into the A site. The tRNA that was in the A site departs from the ribosome via a tunnel The polypeptide enters the E site The tRNA that was in the A site moves to the E site and is released
Selected Answer: The tRNA that was in the A site moves into the P site.
As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs? Answers: The tRNA that was in the P site moves into the A site. The tRNA that was in the A site departs from the ribosome via a tunnel The polypeptide enters the E site The tRNA that was in the A site moves to the E site and is released The tRNA that was in the A site moves into the P site.
Selected Answer: The tRNA that was in the A site moves into the P site.
Which of the following is (are) true of snRNPs? Answers: They act only in the cytosol. They attach introns to exons in the correct order. They are made up of both DNA and RNA. They join together to form a large structure called the spliceosome They bind to splice sites at each end of the exon
Selected Answer: They join together to form a large structure called the spliceosome
Which of the following statements are true about protein synthesis in prokaryotes? Answers: Translation can begin while transcription is still in progress. Unlike eukaryotes, prokaryotes require no initiation or elongation factors Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles. Translation requires antibiotic activity Extensive RNA processing is required before prokaryotic transcripts can be translated.
Selected Answer: Translation can begin while transcription is still in progress.
The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid? Answers: GUA UGG UUC GUG CAU
Selected Answer: UUC
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is Answers: TTT. AAA UUU either UAA or TAA, depending on first base wobble UUA
Selected Answer: UUU
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is Answers: TTT. UUA AAA UUU either UAA or TAA, depending on first base wobble
Selected Answer: UUU
Which of the following nucleotide triplets best represents a codon? Answers: a triplet in the same reading frame as an upstream AUG a triplet at the opposite end of tRNA from the attachment site of the amino acid a sequence in tRNA at the 3' end a triplet separated spatially from other triplets a triplet that has no corresponding amino acid
Selected Answer: a triplet in the same reading frame as an upstream AUG
When does translation begin in prokaryotic cells? Answers: once the pre-mRNA has been converted to mRNA after the 5' caps are converted to mRNA as soon as transcription has begun after a transcription initiation complex has been formed as soon as the DNA introns are removed from the template
Selected Answer: as soon as transcription has begun
Alternative RNA splicing Answers: increases the rate of transcription can allow the production of similar proteins from different RNAs can allow the production of proteins of different sizes from a single mRNA is due to the presence or absence of particular snRNPs. is a mechanism for increasing the rate of transcription.
Selected Answer: can allow the production of proteins of different sizes from a single mRNA
A mutation in which of the following parts of a gene is likely to be most damaging to a cell? Answers: 3' UTR All would be equally damaging 5' UTR exon intron
Selected Answer: exon
A mutation in which of the following parts of a gene is likely to be most damaging to a cell? Answers: All would be equally damaging 5' UTR intron 3' UTR exon
Selected Answer: exon
A mutation in which of the following parts of a gene is likely to be most damaging to a cell? Answers: exon All would be equally damaging 5' UTR 3' UTR intron
Selected Answer: exon
What are polyribosomes? Answers: groups of ribosomes reading a single mRNA simultaneously ribosomes containing more than two subunits multiple copies of ribosomes associated with giant chromosomes aggregations of vesicles containing ribosomal RNA ribosomes associated with more than one tRNA
Selected Answer: groups of ribosomes reading a single mRNA simultaneously
A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that Answers: there are termination exons near the beginning of mRNA many noncoding stretches of nucleotides are present in mRNA many nucleotides are needed to code for each amino acid. nucleotides break off and are lost during the transcription process. there is redundancy and ambiguity in the genetic code
Selected Answer: many noncoding stretches of nucleotides are present in mRNA
If A, B, and C are all required for growth, a strain that is mutant for the gene encoding enzyme A would be able to grow on which of the following media? Answers: minimal medium supplemented with nutrient "B" only minimal medium minimal medium supplemented with nutrient "A" only minimal medium supplemented with nutrient "C" only minimal medium supplemented with nutrients "A" and "C"
Selected Answer: minimal medium supplemented with nutrient "B" only
Sickle-cell disease is probably the result of which kind of mutation? Answers: both B and D point nondisjunction frameshift nonsense
Selected Answer: point
A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that Answers: the ribosome will skip a codon every time a UUU is encountered. the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons None of the above will occur; the cell will recognize the error and destroy the tRNA none of the proteins in the cell will contain phenylalanine proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
Selected Answer: proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
