Ch 17
- 1.
Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because
- A.
RNA is much more stable than DNA
- B.
RNA acts as an expendable copy of the genetic material
- C.
Only one mRNA molecule can be transcribed from a single gene, lowering the potential rate of gene expression
- D.
TRNA, rRNA and others are not transcribed
- E.
MRNA molecules are subject to mutation but DNA is not
Correct Answer
B. RNA acts as an expendable copy of the genetic material -
- 2.
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because
- A.
Enzymes are made of DNA, and affected individuals lack DNA polymerase
- B.
Many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA
- C.
Certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors
- D.
Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes
- E.
Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies
Correct Answer
D. Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes -
- 3.
The "universal" genetic code is now know to have exceptions. Evidence for this could be found if which of the following is true?
- A.
If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA
- B.
If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide
- C.
If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only)
- D.
If several codons are found to translate to the same amino acid, such as serine
- E.
If a single mRNA molecule is found to translate to more than one polypeptide where there are two or more AUG sites
Correct Answer
C. If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only) -
- 4.
RNA polymerase moves in which direction along the DNA?
- A.
5' --> 3' along the template strand
- B.
5' --> 3' along the double-stranded DNA
- C.
3' --> 5' along the template strand
- D.
3' --> 5' along the coding strand
- E.
3' --> 5' along the coding (sense) strand
Correct Answer
C. 3' --> 5' along the template strand -
- 5.
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which might this illustrate?
- A.
Any mutation in the sequence is selected against
- B.
The sequence evolves very rapidly
- C.
The sequence does not mutate
- D.
The sequence is found in many but not all promoters
- E.
The sequence is transcribed at the start of every gene
Correct Answer
A. Any mutation in the sequence is selected against -
- 6.
A transcription unit that is 8000 nucleotides long may use 1200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that
- A.
There is redundancy and ambiguity in the genetic code
- B.
Many nucleotides are needed to code for each amino acid
- C.
Nucleotides break off and are lost during the transcription process
- D.
Many noncoding stretches of nucleotides are present in mRNA
- E.
There are termination exons near the beginning of mRNA
Correct Answer
D. Many noncoding stretches of nucleotides are present in mRNA -
- 7.
In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
- A.
The sequence of the intron that immediately precedes each exon
- B.
The various domains of the polypeptide product
- C.
The number of polypeptides making up the functional protein
- D.
The number of restriction enzyme cutting sites
- E.
The number of start sites for transcription
Correct Answer
B. The various domains of the polypeptide product -
- 8.
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
- A.
None of the proteins in the cell will contain phenylalanine
- B.
The cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons
- C.
Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU
- D.
The ribosome will skip a codon every time a UUU is encountered
- E.
None of the above will occur; the cell will recognize the error and destroy the tRNA
Correct Answer
C. Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU -
- 9.
From the following list, which is the first event in translation in eukaryotes?
- A.
The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
- B.
Base pairing of the activated methionine - tRNA to AUG of the messenger RNA
- C.
The larger ribosomal subunit binds to smaller ribosomal subunits
- D.
Covalent bonding between the first two amino acids
- E.
Elongation of the polypeptide
Correct Answer
A. The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA -
- 10.
Why might a point mutation in DNA make a difference in the level of protein's activity?
- A.
It might result in a chromosomal translocation
- B.
It might exchange one stop codon for another stop codon
- C.
It might exchange one serine codon for a different serine codon
- D.
It might substitute the N terminus of the polypeptide for the C terminus
- E.
It might substitute an amino acid in the active site
Correct Answer
E. It might substitute an amino acid in the active site -
- 11.
Which of the following is true for both prokaryotic and eukaryotic gene expression?
- A.
After transcription, a 3ʹ poly-A tail and a 5ʹ cap are added to mRNA
- B.
Translation of mRNA can begin before transcription is complete
- C.
RNA polymerase binds to the promoter region to begin transcription
- D.
MRNA is synthesized in the 3ʹ → 5ʹ direction
- E.
The mRNA transcript is the exact complement of the gene from which it was copied
Correct Answer
C. RNA polymerase binds to the promoter region to begin transcription -
- 12.
Which of the following help(s) to stabilize mRNA by inhibiting its degradation?
- A.
TATA box
- B.
Spliceosomes
- C.
Introns
- D.
5ʹ cap and poly (A) tail
- E.
RNA polymerase
Correct Answer
D. 5ʹ cap and poly (A) tail -
- 13.
A mutation in which of the following parts of a gene is likely to be most damaging to a cell?
- A.
Intron
- B.
Exon
- C.
5ʹ UTR
- D.
3ʹ UTR
- E.
All would be equally damaging.
Correct Answer
B. Exon -
- 14.
The tRNA shown in Figure 17.4 has its 3ʹ end projecting beyond its 5ʹ end. What will occur at this 3ʹ end?
- A.
The codon and anticodon complement one another.
- B.
The amino acid binds covalently
- C.
The excess nucleotides (ACCA) will be cleaved off at the ribosome
- D.
The small and large subunits of the ribosome will attach to it
- E.
The 5ʹ cap of the mRNA will become covalently bound
Correct Answer
B. The amino acid binds covalently -
- 15.
What are polyribosomes?
- A.
Groups of ribosomes reading a single mRNA simultaneously
- B.
Ribosomes containing more than two subunits
- C.
Multiple copies of ribosomes associated with giant chromosomes
- D.
Aggregations of vesicles containing ribosomal RNA
- E.
Ribosomes associated with more than one tRNA
Correct Answer
A. Groups of ribosomes reading a single mRNA simultaneously -
- 16.
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?
- A.
An assembled ribosome with a polypeptide attached to the tRNA in the P site
- B.
Separated ribosomal subunits, a polypeptide, and free tRNA
- C.
An assembled ribosome with a separated polypeptide
- D.
Separated ribosomal subunits with a polypeptide attached to the tRNA
- E.
A cell with fewer ribosomes
Correct Answer
A. An assembled ribosome with a polypeptide attached to the tRNA in the P site -
- 17.
What is the effect of a nonsense mutation in a gene?
- A.
It changes an amino acid in the encoded protein
- B.
It has no effect on the amino acid sequence of the encoded protein
- C.
It introduces a premature stop codon into the mRNA
- D.
It alters the reading frame of the mRNA
- E.
It prevents introns from being excised
Correct Answer
C. It introduces a premature stop codon into the mRNA -
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