Chapter 14
Which of the following processes only occurs in eukaryotic gene expression?
A poly-A tail is added to the 3' end of an mRNA, and a cap is added to the 5' end.
Which of the following statements correctly defines the process of gene expression?
Gene expression is the process by which DNA directs the synthesis of proteins.
Which of the following is a function of a poly-A tail in mRNA?
It helps protect the mRNA from degradation by hydrolytic enzymes.
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA known as pre-mRNA?
RNA polymerase II
Which of the following statements is correct regarding protein synthesis in prokaryotes and eukaryotes?
Translation can begin while transcription is still in progress in prokaryotes, but not in eukaryotes.
to the right of the template strand
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
UUU.
During transcription of the DNA in the figure above, where would the promoter be located?
to the right of the template strand
Examine the simple metabolic pathway in the figure above. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
2
Examine the table of codons in the figure above. A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be
3'-AAA-GAA-TAA-CAA-5'.
A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. The corresponding codon for the mRNA transcribed is
3'-UCA-5'.
Using the figure below, identify a 5' → 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys.
5′-CTTCGGGAA-3′
Which component is not directly involved in translation?
DNA
Which of the following is not true of RNA processing?
Exons are cut out before mRNA leaves the nucleus.
Which of the following statements correctly describes the function of a signal peptide?
It assists in the translocation of polypeptides across the ER membrane.
Which of the following is not true of a codon?
It extends from one end of a tRNA molecule.
Which of the following statements best describes the function of the TATA box in eukaryotic promoters?
It is the recognition site for a specific transcription factor.
What must happen to a newly made polypeptide before it can be secreted from a cell?
Its signal sequence must target it to the ER, after which it goes to the Golgi.
A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. What would be a potential consequence for a cell in which this happens? Remember that phenylalanine may be encoded by multiple codons.
Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
Use the following model of a eukaryotic transcript to answer the question. E1-4 refer to the exons, and I1-3 refer to the introns in the pre-mRNA transcript. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might be the result of this removal?
Removal of the 5' UTR also removes the 5' cap, so the mRNA may be quickly degraded by hydrolytic enzymes.
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find?
The molecule is degraded by hydrolytic enzymes because it is no longer protected at the 5' end and the 3' end.
Which of the following DNA mutations is likely to have the most negative effect on the protein it specifies?
a base-pair deletion
Which of the following mutations would be most likely to have a harmful effect on an organism?
a single nucleotide insertion downstream of, and close to, the start of the coding sequence
Which of the following descriptions of nucleotide triplets best represents a codon?
a triplet in the same reading frame as an upstream AUG
How do small RNAs in the spliceosome initiate the splicing of the pre-mRNA?
by base pairing to specific sites along the intron
The anticodon of a particular tRNA molecule is
complementary to the corresponding mRNA codon.
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) already in the ribosome. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?
newly formed polypeptide
The process of translation in both prokaryotes and eukaryotes requires tRNAs, amino acids, and ribosomal subunits. Which of the following components must also be present for translation to proceed?
protein factors and GTP
In eukaryotic cells, transcription cannot begin until
several transcription factors have bound to the promoter.
