BIO 171 EXAM 4 REVIEW
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base? -One of the daughter cells, but not the other, would have radioactive DNA. -Neither of the two daughter cells would be radioactive. -All four bases of the DNA would be radioactive. -DNA in both daughter cells would be radioactive.
-DNA in both daughter cells would be radioactive.
Which of the following statements correctly describes the primary difference between enhancers and proximal control elements? -Enhancers are transcription factors; proximal control elements are DNA sequences. -Enhancers improve transcription; proximal control elements inhibit transcription. -Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter. -Enhancers are DNA sequences; proximal control elements are proteins.
-Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter.
Which of the following is most critical for the association between histones and DNA? -Histones are small proteins. -Histones are highly conserved (that is, histones are very similar in every eukaryote). -There are at least five different histone proteins in every eukaryote. -Histones are positively charged.
-Histones are positively charged.
A mutation in E. coli results in a molecule known as a "super-repressor" because the operon is permanently repressed. Which of the following describes the most likely effect of the mutation on the repressor protein? -It cannot bind to the operator. -It cannot make a functional repressor. -It cannot bind to the inducer. -It makes a repressor that binds CAP.
-It cannot bind to the inducer.
What does it mean when we say the genetic code is redundant? -A single codon can specify the addition of more than one amino acid. -The genetic code is different for different domains of organisms. -The genetic code is universal (the same for all organisms). -More than one codon can specify the addition of the same amino acid.
-More than one codon can specify the addition of the same amino acid.
In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation? -Additional proofreading will occur. -No replication fork will be formed. -Replication will occur via RNA polymerase alone. -Replication will require a DNA template from another source.
-No replication fork will be formed.
How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why? -Only a single amino acid could change, because the reading frame is unaffected. -The amino acid sequence would be substantially altered, because the reading frame would change with a single base substitution. -All amino acids following the substitution would be affected, because the reading frame would be shifted. -It is not possible for a single base substitution to affect protein structure, because each codon is three bases long.
-Only a single amino acid could change, because the reading frame is unaffected.
For a repressible operon to be transcribed, which of the following conditions must occur? -RNA polymerase must bind to the promoter and a corepressor must be present. -RNA polymerase and active repressor must occupy the promoter. -RNA polymerase must bind to the promoter, and the repressor must be inactive. -RNA polymerase must bind the inducer, and the repressor must be inactive.
-RNA polymerase must bind to the promoter, and the repressor must be inactive.
What is meant by the description "antiparallel" regarding the strands that make up DNA? -The twisting nature of DNA creates nonparallel strands. -The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand. -Base pairings create unequal spacing between the two DNA strands. -One strand contains only purines and the other contains only pyrimidines.
-The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
If a researcher moves the repressor gene (lacI) and its promoter, to a position at some several thousand base pairs away from its normal position, which of the following describes the most likely effect on the lac operon? -The repressor will no longer bind to the operator. -The repressor will no longer bind to the inducer. -The lac operon will be expressed continuously. -The lac operon will function normally.
-The lac operon will function normally.
What is the difference between the leading strand and the lagging strand in DNA replication? -The leading strand is synthesized in the 3' → 5' direction in a discontinuous fashion, while the lagging strand is synthesized in the 5' → 3' direction in a continuous fashion. -The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction. -The leading strand requires an RNA primer, whereas the lagging strand does not. -There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.
-The leading strand is synthesized continuously in the 5' → 3' direction, while the lagging strand is synthesized discontinuously in the 5' → 3' direction.
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its cap and poly-A tail. Which of the following would you expect her to find? -The mRNA is quickly converted into a ribosomal subunit. -The cell adds a new poly-A tail to the mRNA. -The mRNA attaches to a ribosome and is translated, but more slowly. -The molecule is digested by enzymes because it is not protected at the 5' end.
-The molecule is digested by enzymes because it is not protected at the 5' end.
If a researcher moves the operator to the far end of the operon, which of the following processes would likely occur when the cell is exposed to lactose? -The inducer will no longer bind to the repressor. -The repressor will no longer bind to the operator. -The operon will never be transcribed. -The genes of the lac operon will be transcribed continuously.
-The operon will never be transcribed.
A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a fluorescent probe to follow it. Later she finds that the introduced strands separate into single-stranded RNAs and she hypothesizes that the molecules is acting as an miRNA. Which of the following pieces of evidence would support her claim? -The degradation rate of the single strand is slower than that of other cellular mRNA's. -The rate of accumulation of the polypeptide encoded by the target mRNA is reduced. -The amount of the RNA she introduced increases due to transcription. -After separating the strands she introduced shut down all translation.
-The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs? -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 moves to the E site and is released. -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 into the P site.
Which of the following changes in conditions results in an increase in cAMP receptor protein (CRP) mediated initiation of transcription? -an increase in glucose and an increase in the repressor -a decrease in glucose and an increase in cAMP -an increase in glucose and a decrease in cAMP -a decrease in glucose and a decrease in the repressor
-a decrease in glucose and an increase in cAMP
Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. These results best support which of the following conclusions. -the initial heat treatment was unsuccessful -splitting the culture revived the pathogenic bacteria -non-pathogenic bacteria were transformed by pathogenic capsule proteins -a substance had been transferred from pathogenic to nonpathogenic bacteria
-a substance had been transferred from pathogenic to nonpathogenic bacteria
Which of the following nucleotide triplets best represents a codon? -a triplet separated spatially from other triplets -a triplet that has no corresponding amino acid -a triplet at the opposite end of tRNA from the attachment site of the amino acid -a triplet in the same reading frame as an upstream AUG -a sequence in tRNA at the 3' end
-a triplet in the same reading frame as an upstream AUG
Post-translational modifications of proteins may include the _____. -removal of introns -addition of a 5' cap -addition of a poly-A tail -addition of carbohydrates to form a glycoprotein
-addition of carbohydrates to form a glycoprotein
The release factor (RF) _____. -binds to the stop codon in the A site in place of a tRNA -releases the amino acid from its tRNA to allow the amino acid to form a peptide bond -supplies a source of energy for termination of translation -releases the ribosome from the ER to allow polypeptides into the cytosol
-binds to the stop codon in the A site in place of a tRNA
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following? -the evolution of telomerase enzyme -DNA polymerase that cannot replicate the leading strand template to its 5' end -gaps left at the 5' end of the lagging strand -gaps left at the 3' end of the lagging strand because of the need for a primer
-gaps left at the 5' end of the lagging strand
A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA. -the same size as; smaller than -larger than; the same size as -larger than; smaller than -the same size as; larger than
-larger than; the same size as
Which of the following characteristics of gene expression allows bacteria to quickly change protein synthesis patterns in response to environmental changes? -mRNAs that are produced are short-lived and degraded within a few minutes of being synthesized. -mRNA have long lifespans, allowing the bacteria to use them many times for translation. -mRNA is stored for later use when it is needed later. -Operons are activated in the presence of transcription factors.
-mRNAs that are produced are short-lived and degraded within a few minutes of being synthesized.
In E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act? -nuclease, DNA polymerase III, RNA primase -helicase, DNA polymerase I, DNA ligase -DNA ligase, nuclease, helicase -nuclease, DNA polymerase I, DNA ligase
-nuclease, DNA polymerase I, DNA ligase
After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait? -evidence that DNA was passed from the heat-killed strain to the living strain -evidence that protein passed from the heat-killed strain to the living strain -especially bright phosphorescence in the living strain -phosphorescence in descendants of the living cells
-phosphorescence in descendants of the living cells
From the following list, which is the first event in translation in eukaryotes? -elongation of the polypeptide -base pairing of activated methionine-tRNA to AUG of the messenger RNA -the larger ribosomal subunit binds to smaller ribosomal subunits -covalent bonding between the first two amino acids -the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
-the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
Under what conditions does the trp repressor block transcription of the trp operon? -when the repressor binds to the inducer -when the repressor binds to tryptophan -when the repressor is not bound to tryptophan -when the repressor is not bound to the operator
-when the repressor binds to tryptophan
Put the following events of elongation in prokaryotic translation in chronological order. 1.Binding of mRNA with small ribosomal subunit 2. Recognition of initiation codon 3. Complementary base pairing between initiator codon and anticodon of initiator tRNA 4. Base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5. Attachment of the large subunit 1, 2, 3, 4, 5 2, 1, 4, 3, 5 5, 4, 3, 2, 1 1, 2, 3, 5, 4
1, 2, 3, 5, 4
A sample of double-stranded DNA contains 28% thymine. Approximately what percent of the nucleotides in this sample will be guanine? 8% 16% 22% 72%
22%
RNA polymerase moves in which direction along the DNA? 3' → 5' along the template strand 3' → 5' along the coding (sense) strand 5' → 3' along the template strand 3' → 5' along the coding strand 5' → 3' along the double-stranded DNA
3' → 5' along the template strand
Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? 8% 16% 42% 58%
8%
Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression? -mRNA, tRNA, and rRNA are transcribed. -RNA polymerase binds to the promoter. -A cap is added to the 5' end of the mRNA. -RNA polymerase requires a primer to elongate the molecule.
A cap is added to the 5' end of the mRNA.
Which of the following is a function of a signal peptide? A) to direct an mRNA molecule into the cisternal space of the ER B) to bind RNA polymerase to DNA and initiate transcription C) to terminate translation of the messenger RNA D) to translocate polypeptides across the ER membrane E) to signal the initiation of transcription
D) to translocate polypeptides across the ER membrane
Much of the human genome does not code for proteins. Which of the following types of DNA are found in these regions of the genome? -DNA that consists only of histone coding sequences -DNA that is translated directly without being transcribed -DNA that is transcribed into several kinds of small RNAs with biological function -DNA that serves as binding sites for reverse transcriptase
DNA that is transcribed into several kinds of small RNAs with biological function
Which of the following mechanisms is commonly used to coordinate the expression of multiple, related genes in eukaryotic cells? -Environmental signals entering the cell cause the genes to rearrange into related sets. -Groups of genes that are expressed together have specific combinations of control elements. -Related genes are organized in operons that share a promoter that controls their expression. -Release of each gene's individual inducing molecule must be coordinated to coordinate gene expression.
Groups of genes that are expressed together have specific combinations of control elements.
Which of the following processes is the best way to determine whether alternative splicing of a given gene occurs? -Compare the size of the DNA within the given gene and a similar gene in a related organism. -Compare the sequences of the given gene and a gene known to undergo alternative splicing. -Isolate the primary transcripts made from the given gene and compare the sequences. -Isolate mRNA from the given gene and compare the sequences
Isolate mRNA from the given gene and compare the sequences
Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukarotes? -DNA from a single gene is replicated and transferred to the cytoplasm, where it serves as a template for protein synthesis. -Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place. -Proteins transfer information from the nucleus to the ribosome, where protein synthesis takes place. -Transfer RNA takes information from DNA directly to a ribosome, where protein synthesis takes place.
Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.
An enzyme that helps relieve the strain on DNA ahead of the replication fork by breaking, swiveling and rejoining DNA strands -Topoisomerase -Helicase -Single-strand binding proteins -DNA polymerase I
Topoisomerase
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is _____. TTT UUA UUU AAA
UUU
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? -irreversible binding of the repressor to the promoter -reduced transcription of the operon's genes -buildup of a substrate for the pathway controlled by the operon -continuous transcription of the operon's genes
continuous transcription of the operon's genes
What are the coding segments of a stretch of eukaryotic DNA called? introns exons codons replicons decepticons
exons
Which of the following molecules binds with a repressor to alter its conformation and therefore affect its function? -inducer -promoter -transcription factor -cAMP
inducer
In RNA processing, the noncoding segments of nucleic acid lie between coding regions are called -exons -introns -poly-A tail -5' cap
introns
According to the central dogma, what molecule should go in the blank?DNA → _____ → Proteins mtDNA rRNA mRNA tRNA
mRNA
Which of the following processes is a single stranded RNA of about 22 nucleotides that, when it forms a complementary complex with a mRNA, leads to the blocking of translation or degradation of the mRNA? -RNAi -microRNAs -RNA blocking -siRNAs
microRNAs
Which of the following is an example of post-transcriptional control of gene expression? -the addition of acetyl groups to the histone tails in chromatin -the binding of transcription factors to a promoter -the removal of introns and alternative splicing of exons -All of the above
the removal of introns and alternative splicing of exons
