BIO 111- Chapter 14
What is the effect of a nucleotide-pair substitution that results in a nonsense mutation in a gene?
It introduces a premature stop codon into the mRNA.
Examine the table of codons in the figure above. What amino acid sequence will be produced based on the following mRNA codon sequence
met-ser-ser-leu-ser-leu
During transcription of the DNA in the figure above, where would the promoter be located?
to the right of the template strand
In which direction does RNA polymerase move along the DNA?
3' to 5' along the template strand
Which component is NOT directly involved in translation?
DNA
Using the table on the left, identify a polypeptide sequence if the DNADNA template strand for an mRNA is 5′−CTGAGGCATGCC−3′
Gly-Met-Pro-Gln
What is the function of the release factor in translation?
It binds to the stop codon in the A site in place of a tRNA.
Which of the following is true of a codon?
It can be either in DNA or in RNA.
The figure above represents a tRNA molecule that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?
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.
What is a ribozyme?
a biological catalyst made of RNA, an RNA with enzymatic activity
Which of the following mutations is most likely to cause a phenotypic change?
a single nucleotide deletion in an exon coding for an active site of a protein
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
The flow of information in a cell proceeds in what sequence?
from DNA to RNA to protein
After an RNA molecule is transcribed from a eukaryotic gene, what is removed and what is spliced together to produce an mRNA molecule with a continuous coding sequence?
introns ... exons
Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
several transcription factors
Which of the following events in translation is the first to occur in eukaryotes?
the small subunit of the ribosome recognizing and attaching to the 5' cap of mRNA
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'
Which of these is currently considered the best definition of a gene?
A gene codes for either a polypeptide or an RNA molecule.
The genetic code is essentially the same for all organisms. Based on this information, one can logically assume which of the following statements to be correct?
A gene from an organism can theoretically be expressed by any other organism.
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.
A part of the promoter, called the TATA box, is said to be highly conserved in many different organisms through evolution. Which of the following correctly describes why this is the case?
Any mutation in the sequence is selected against.
In what way could a point mutation in DNA make a difference in the function of a protein
It might substitute a different amino acid in the protein, which could change its function.
Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying the amino acid leucine, Leu). What will be the effect on the translation of polypeptides in this cell?
One altered tRNA molecule will have little effect because it will compete with many "normal" ones.
The tRNA shown in the figure above has its 3' end projecting beyond its 5' end. Which of the following will occur at this 3' end?
The amino acid will bind covalently.
In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?
The entire template molecule is represented in the product.
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.
Which of the following DNA mutations is likely to have the most negative effect on the protein it specifies?
a base-pair deletion
A codon consists of __________ bases and specifies which __________ will be inserted into the polypeptide chain.
three ... amino acid
Examine the simple metabolic pathway above. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
2
The anticodon loop of the first tRNA that will complement this mRNA is
3'-GGC-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'.
Given the locally unwound double strand of DNA in the figure above, in which direction and on what strand does the RNA polymerase move during transcription?
3'→5' along the template strand
Which components of the previous molecule will also be found in mRNA in the cytosol?
5' UTR E1 E2 E3 E4 UTR 3'
Examine the table of codons in the figure above. 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?
5'-TTT-CCC-AAA-GGG-TTT-CCC
The nitrogenous base adenine is found in all members of which of the following groups of molecules?
ATP, RNA, and DNA
Which of the following statements correctly compares transcription in prokaryotes and eukaryotes?
Bacteria have one type of RNA polymerase, whereas eukaryotes have at least three.
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. Where does tRNA #2 move to after this bonding of lysine to the polypeptide?
E site
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 statements correctly describes alternative RNA splicing?
It can allow the production of different protein products from a single mRNA.
Which of the following is a function of a poly-A tail in mRNA?
It helps protect the mRNA from degradation by hydrolytic enzymes.
What happens to the cut-out intron after alternative RNA splicing?
It is rapidly degraded.
Where does RNA polymerase begin transcribing a gene into mRNA?
It starts after a certain nucleotide sequence called a promoter.
What is the function of RNA polymerase?
It unwinds the double helix and adds nucleotides to a growing strand of RNA
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 eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. Which of the following statements best explains this fact?
Many noncoding stretches of nucleotides are present in eukaryotic DNA.
Which of the following is true of RNA processing?
Nucleotides are added at both ends of the RNA
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.
A mutation in a cell results in a structural change in the signal-recognition particle (SRP) so that it does not bind to the translocation complex in the ER correctly. Which of the following processes will occur because of this mutation?
Proteins produced during translation that are destined for the ER will not be translocated into the ER.
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
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.
A eukaryotic mutation upstream of a particular gene has been identified that changes the sequence of the TATA box to GATA. How would you predict that this mutation would affect the transcription of this gene?
Transcription factor binding would be reduced or eliminated, and transcription of the gene would decrease dramatically.
In the 1920s, Hermann Muller discovered that X-rays caused genetic changes in the fruit fly Drosophila. In a related series of experiments in the 1940s, other scientists discovered that other types of chemicals have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why is it necessary to test for its ability to cause mutation?
We want to prevent any chance that it might cause mutations.
What is the direct result of a mutagen?
a change in the sequence of DNA
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the most likely result of this mutation in the protein product?
a polypeptide missing an amino acid
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
Examine the simple metabolic pathway above. A mutation results in a defective enzyme 1. Which of the following results would be a consequence of that mutation?
an accumulation of A and no production of B and C
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 sets of structures would you be able to isolate from the cell?
an assembled ribosome with a polypeptide attached to the tRNA in the P site
Accuracy in the translation of mRNA into the sequence of amino acids in a polypeptide depends on specificity in which of the following characteristics?
bonding of the anticodon to the codon and the attachment of amino acids to tRNAs
Which of the following types of mutations could result in a frameshift mutation?
either an insertion or a deletion of a base
Garrod hypothesized that inherited diseases such as alkaptonuria, the inability to metabolize the chemical alkapton, occur because
genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
What type of bonding is responsible for maintaining the shape of the tRNA molecule in the figure above?
hydrogen bonding between base pairs
The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following statements is true?
if UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only)
Use the following model of a eukaryotic transcript to answer the question. E 1-4 refer to the exons, and I 1-3 refer to the introns in the pre-mRNA transcript. 5' UTR E 1 I 1 E 2 I 2 E 3 I 3 E 4 UTR 3' Suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5' end of intron 1 (I 1). Which of the following results might occur?
inclusion of I1 in the mRNA
Examine the table of codons in the figure above. What amino acid sequence will be produced based on the following mRNA codon sequence?5'-AUG-UCU-UCG-UUA-UCC-UUG-3'
met-ser-ser-leu-ser-leu
Examine the simple metabolic pathway above. If A, B, and C are all substances required for growth of the organism that carries out this pathway, a strain that is mutant for the gene encoding enzyme 1 would be able to grow on which of the following media?
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) already in the ribosome. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?
newly formed polypeptide
During the process of alternative RNA splicing, where on a pre-mRNA transcript does a spliceosome bind?
on certain sequences of an intron
The dipeptide that will form will be
proline-threonine
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
Which one of the following is true of tRNAs?
tRNAs carry amino acids to the ribosome during translation.
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that
the rules for base pairing between the third base of a codon and tRNA are flexible.
