Question 1

Which molecule allows the release of mRNA from a stalled ribosome?

Accepted Answer

A)  miRNA 
B)  snoRNA 
C)  incRNA 
D)  tmRNA 
E)  siRNA 
A)  miRNA 
B)  snoRNA 
C)  incRNA 
D)  tmRNA 
E)  siRNA

Question 2

List three differences between prokaryotic and eukaryotic translation.

Accepted Answer

Prokaryotic and eukaryotic translation a

Question 3

There are _____ different codons, which encode 20 amino acids and 3 stop codons.

Accepted Answer

A)  16 
B)  20 
C)  23 
D)  61 
E)  64 
A)  16 
B)  20 
C)  23 
D)  61 
E)  64

Question 4

Describe the events in prokaryotic translation elongation.

Accepted Answer

During prokaryotic translation elongatio

Question 5

The antibiotic streptomycin binds to the 30S subunit in bacteria and interferes with translation. Streptomycin resistance (SmR) can occur through mutation in the rpsL gene, which encodes the ribosomal protein S12. The antibiotic can no longer bind to the altered protein, so translation can occur without interference from the antibiotic. However, in the absence of streptomycin, many SmR strains of bacteria grow less well than the non-mutant streptomycin-sensitive (SmS) bacteria.
a. Propose a model for why SmR bacteria grow better than SmS bacteria in the presence of streptomycin but not as well in the absence of streptomycin.
b. During translation, an incorrect amino acid is occasionally incorporated into the polypeptide chain-that is, the amino acid added does not correspond to the codon at that location in the mRNA. You develop an assay that can assess this rate of incorrect amino acid incorporation and thereby estimate the accuracy of translation in bacteria. You find that SmR bacteria are more accurate than SmS bacteria in this experiment. How might this observation affect your model above?

Accepted Answer

a. The model for why SmR bacteria grow b

Question 6

Use the following to answer questions 
Refer to the following sequence:
5' ...GGAGCUCGUUGUAUU... 3'
-This sequence is RNA because:

Accepted Answer

A)  it is single stranded. 
B)  it contains U (uracil) and no T (thymine). 
C)  it runs in a 5'to 3'direction. 
D)  it codes for amino acids . 
E)  it is a small molecule. 
A)  it is single stranded. 
B)  it contains U (uracil) and no T (thymine). 
C)  it runs in a 5'to 3'direction. 
D)  it codes for amino acids . 
E)  it is a small molecule.

Question 7

A yeast strain was exposed to a chemical mutagen. As expected, exposure to a mutagen resulted in a DNA sequence change in an essential gene you examined. Yet this mutation did not result in any lethal phenotype. How do you explain this apparent discrepancy?

Accepted Answer

There are several possible explanations

Question 8

The genetic code is said to be "degenerate" because:

Accepted Answer

A)  there are more codons than amino acids. 
B)  there are more amino acids than codons. 
C)  different organisms use different codons to encode the same amino acid. 
D)  some codons specify more than one amino acid. 
E)  there are more tRNAs than amino acids. 
A)  there are more codons than amino acids. 
B)  there are more amino acids than codons. 
C)  different organisms use different codons to encode the same amino acid. 
D)  some codons specify more than one amino acid. 
E)  there are more tRNAs than amino acids.

Question 9

An auxotrophic E. coli strain requires adenine to grow because of a mutation in a gene for an adenine synthesis enzyme. The following shows part of the wild-type and mutant alleles of the gene, including the start codon. The bottom strand is the template for transcription. $$\begin{array} { c c } 
\text { ade } 1 ^ { + } \text {wild-type allele } & \text { ade1 } ^ { - } \text {mutant allele } \
\text { 5'...TTATGGGCAAGATCCCA...3' } &  \text { 5'....TTA TGGGCTAGATCCCA...3' } \
\text { 3'...AATACCCGTTCTAGGGT...5' } & \text { 3'...AATATGGGCTAGATCCCA...3' }
\end{array}$$ 
-Explain why the mutant lysine tRNA allele from the previous question might affect overall cell growth.

Accepted Answer

The mutant lysine tRNA allele might affe

Question 10

Codons that specify the same amino acid are said to be:

Accepted Answer

A)  wobbly. 
B)  isoaccepting. 
C)  hypothetical. 
D)  synonymous. 
E)  anonymous. 
A)  wobbly. 
B)  isoaccepting. 
C)  hypothetical. 
D)  synonymous. 
E)  anonymous.

Question 11

During initiation, the _____ subunit is the first part of the ribosome to associate with the mRNA.

Accepted Answer

A)  small 
B)  large 
C)  intermediary 
D)  secondary 
E)  tertiary 
A)  small 
B)  large 
C)  intermediary 
D)  secondary 
E)  tertiary

Question 12

Use the following to answer questions :  
-After the peptide bond forms, what will happen next?

Accepted Answer

A)  tRNA A will be carrying the polypeptide and it will shift to the P site. 
B)  tRNA A will be carrying the polypeptide and it will shift to the A site. 
C)  tRNA B will be carrying the polypeptide and it will shift to the P site. 
D)  tRNA B will be carrying the polypeptide and it will shift to the A site. 
E)  Ribosome disassembles to release the tRNAs and to allow new tRNA to enter. 
A)  tRNA A will be carrying the polypeptide and it will shift to the P site. 
B)  tRNA A will be carrying the polypeptide and it will shift to the A site. 
C)  tRNA B will be carrying the polypeptide and it will shift to the P site. 
D)  tRNA B will be carrying the polypeptide and it will shift to the A site. 
E)  Ribosome disassembles to release the tRNAs and to allow new tRNA to enter.

Question 13

Use the following to answer questions  
-If the bottom strand of the DNA serves as the template, the amino acid sequence of the protein produced from the RNA would be:

Accepted Answer

A)  met-leu-ser. 
B)  arg-val-his. 
C)  thr-ile-phe. 
D)  pro-gly-trp. 
E)  lys-val-his. 
A)  met-leu-ser. 
B)  arg-val-his. 
C)  thr-ile-phe. 
D)  pro-gly-trp. 
E)  lys-val-his.

Question 14

An auxotrophic E. coli strain requires adenine to grow because of a mutation in a gene for an adenine synthesis enzyme. The following shows part of the wild-type and mutant alleles of the gene, including the start codon. The bottom strand is the template for transcription. $$\begin{array} { c c } 
\text { ade } 1 ^ { + } \text {wild-type allele } & \text { ade1 } ^ { - } \text {mutant allele } \
\text { 5'...TTATGGGCAAGATCCCA...3' } &  \text { 5'....TTA TGGGCTAGATCCCA...3' } \
\text { 3'...AATACCCGTTCTAGGGT...5' } & \text { 3'...AATATGGGCTAGATCCCA...3' }
\end{array}$$
- E. coli strains that have both the original ade1- mutant allele shown above and a mutant allele for a gene that encodes a lysine tRNA are able to make some normal ade1 enzyme. The mutant lysine tRNA allele makes tRNA that has one base that is different from the wild-type tRNA. Explain how the lysine tRNA mutation allows synthesis of the normal ade1 enzyme.

Accepted Answer

The mutant lysine tRNA allele likely all

Question 15

A tRNA anticodon is 5' GCU 3'. What amino acid does it carry?

Accepted Answer

A)  ala 
B)  arg 
C)  ser 
D)  pro 
E)  thr 
A)  ala 
B)  arg 
C)  ser 
D)  pro 
E)  thr

Question 16

Which of the following mechanisms specifically allows detection and rapid degradation of mRNA containing a premature termination codon?

Accepted Answer

A)  RNA interference 
B)  no-go decay 
C)  nonsense-mediated mRNA decay 
D)  transfer-messenger RNA mediated ribosomal removal 
E)  nonstop mRNA decay 
A)  RNA interference 
B)  no-go decay 
C)  nonsense-mediated mRNA decay 
D)  transfer-messenger RNA mediated ribosomal removal 
E)  nonstop mRNA decay

Question 17

The function of aminoacyl-tRNA synthetases is to:

Accepted Answer

A)  transcribe tRNA genes. 
B)  match tRNA anticodons and mRNA codons at the ribosome. 
C)  attach appropriate amino acids to corresponding tRNAs. 
D)  form the peptide bond between amino acids at the ribosome. 
E)  synthesize and transport amino acids to the ribosomes. 
A)  transcribe tRNA genes. 
B)  match tRNA anticodons and mRNA codons at the ribosome. 
C)  attach appropriate amino acids to corresponding tRNAs. 
D)  form the peptide bond between amino acids at the ribosome. 
E)  synthesize and transport amino acids to the ribosomes.

Question 18

Prokaryotic ribosomes are inhibited by antibiotics like tetracyclines. As eukaryotes, humans are unaffected by these antibiotics. However, ribosomes within human mitochondria more closely resemble prokaryotic ribosomes than eukaryotic ribosomes. Why aren't tetracyclines more toxic to humans if they can, in theory, inhibit mitochondrial ribosomes?

Accepted Answer

Tetracyclines and other antibiotics that

Question 19

What was Beadle and Tatum's definition of a gene? Give a modern definition and explain how it differs from that of Beadle and Tatum.

Accepted Answer

Beadle and Tatum's definition of a gene

Question 20

Use the following to answer questions 
Refer to the following sequence:
5' ...GGAGCUCGUUGUAUU... 3'
-The sequence 5' ...GGAGCUCGUUGUAUU... 3'is changed to 5'… GGAGACUCGUUGUAUU… 3'. What would be the effect on the amino acid sequence?

Accepted Answer

A)  There would be no effect on the amino acid sequence. 
B)  This is an insertion mutation so there would be a premature stop codon. 
C)  The amino acid sequence would be asn-thr-thr-thr-leu. 
D)  The amino acid sequence would be thr-ser-tyr-leu-asn. 
E)  The amino acid sequence would be gly-asp-ser-leu-tyr. 
A)  There would be no effect on the amino acid sequence. 
B)  This is an insertion mutation so there would be a premature stop codon. 
C)  The amino acid sequence would be asn-thr-thr-thr-leu. 
D)  The amino acid sequence would be thr-ser-tyr-leu-asn. 
E)  The amino acid sequence would be gly-asp-ser-leu-tyr.

Exam 15: The Genetic Code and Translation

Which molecule allows the release of mRNA from a stalled ribosome?

List three differences between prokaryotic and eukaryotic translation.

There are _____ different codons, which encode 20 amino acids and 3 stop codons.

Describe the events in prokaryotic translation elongation.

Use the following to answer questions Refer to the following sequence: 5' ...GGAGCUCGUUGUAUU... 3' -This sequence is RNA because:

A yeast strain was exposed to a chemical mutagen. As expected, exposure to a mutagen resulted in a DNA sequence change in an essential gene you examined. Yet this mutation did not result in any lethal phenotype. How do you explain this apparent discrepancy?

The genetic code is said to be "degenerate" because:

Codons that specify the same amino acid are said to be:

During initiation, the _____ subunit is the first part of the ribosome to associate with the mRNA.

Use the following to answer questions : -After the peptide bond forms, what will happen next?

Use the following to answer questions -If the bottom strand of the DNA serves as the template, the amino acid sequence of the protein produced from the RNA would be:

A tRNA anticodon is 5' GCU 3'. What amino acid does it carry?

Which of the following mechanisms specifically allows detection and rapid degradation of mRNA containing a premature termination codon?

The function of aminoacyl-tRNA synthetases is to:

What was Beadle and Tatum's definition of a gene? Give a modern definition and explain how it differs from that of Beadle and Tatum.

Use the following to answer questions Refer to the following sequence: 5' ...GGAGCUCGUUGUAUU... 3' -The sequence 5' ...GGAGCUCGUUGUAUU... 3'is changed to 5'… GGAGACUCGUUGUAUU… 3'. What would be the effect on the amino acid sequence?

Introduction to Genetics

Chromosomes and Cellular Reproduction

Basic Principles of Heredity

Sex Determination and Sex-Linked Characteristics

Extensions and Modifications of Basic Principles

Pedigree Analysis, Applications, and Genetic Testing

Linkage, Recombination, and Eukaryotic Gene Mapping

Chromosome Variation

Bacterial and Viral Genetic Systems

DNA: the Chemical Nature of the Gene

Chromosome Structure and Organelle Dna

DNA Replication and Recombination

Transcription

Rna Molecules and Rna Processing

Control of Gene Expression in Prokaryotes

Control of Gene Expression in Eukaryotes

Gene Mutations and Dna Repair

Molecular Genetic Analysis and Biotechnology

Genomics and Proteomics

Epigenetics

Developmental Genetics and Immunogenetics

Cancer Genetics

Quantitative Genetics

Population Genetics

Evolutionary Genetics

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