BIOL 343: Genetics Exam 3 Study Guide

A collection of recombinant vectors that contain fragments of chromosomal DNA is called A. a genomic library. B. a cDNA library. C. a Southern blot. D. both a and b.

A

A key difference between the original Holliday model and the double-strand break model is the way that A. the DNA strands are initially broken. B. branch migration occurs. C. a heteroduplex is formed. D. resolution occurs.

A

Which of the following statements is false? A. All genes encode polypeptides that function as units within proteins. B. Some genes encode RNAs that are never translated. C. Most genes encode mRNAs. D. Some RNAs function within protein-RNA complexes.

A

What is the difference between a charged tRNA versus an uncharged tRNA?

A charged tRNA has an amino acid attached to it

What is the difference between an endonuclease and an exonuclease?

An endonuclease can cleave within a strand and an exonuclease digests a strand, one nucleotide at a time

A mutagen that is a base analog is A. ethyl methanesulfonate (EMS). B. 5-bromouracil. C. UV light. D. proflavin.

B

A mutation that changes a codon into a stop codon is a A. missense mutation. B. nonsense mutation. C. frameshift mutation. D. neutral mutation.

B

A repressor is a ___________ that __________ transcription. A. small effector molecule, inhibits B. small effector molecule, enhances C. regulatory protein, inhibits D. regulatory protein, enhances

B

A uracil-rich sequence occurs at the end of the RNA in A. ρ-dependent termination. B. ρ-independent termination. C. both a and b. D. none of the above.

B

According to the selfish DNA hypothesis, TEs exist because A. they offer the host a selective advantage. B. they have characteristics that allow them to multiply within the chromosomal DNA of living cells. C. they promote the expression of certain beneficial genes. D. all of the above.

B

An advantage of translesion DNA polymerases is they can replicate ____________, but a disadvantage is they ____________. A. very quickly, have low fidelity B. over damaged DNA, have low fidelity C. when resources are limited, are very slow D. over damaged DNA, are very slow

B

For the following five sequences, what is the consensus sequence? 5′-GGGAGCG-3′ 5-GAGAGCG-3′ 5′-GAGTGCG-3′ 5′-GAGAACG-3′ 5′-GAGAGCA-3′ A. 5′-GGGAGCG-3′ B. 5′-GAGAGCG-3′ C. 5′-GAGTGCG-3′ D. 5′-GAGAACG-3′

B

A down promoter mutation causes the promoter of a gene to be like the consensus sequence and transcription. A. less, stimulates B. more, stimulates C. less, inhibits D. more, inhibits

C

A release factor is referred to as a "molecular mimic" because its structure is similar to A. a ribosome. B. an mRNA. C. a tRNA. D. an elongation factor.

C

A repressor is a ___________ that __________ transcription. A. small effector molecule, inhibits B. small effector molecule, enhances C. regulatory protein, inhibits D. regulatory protein, enhances

C

An enhancer is a that the rate of transcription. A. trans-acting factor, increases B. trans-acting factor, decreases C. cis-acting element, increases D. cis-acting element, decreases

C

During the peptidyl transferase reaction, the polypeptide, which is attached to a tRNA in the becomes bound via to an amino acid attached to a tRNA in the . A. A site, several hydrogen bonds, P site B. A site, a peptide bond, P site C. P site, a peptide bond, A site D. P site, several hydrogen bonds, A site

C

For the Igf2 gene, where do de novo methylation and maintenance methylation occur? A. de novo methylation occurs in sperm and maintenance methylation occurs in egg cells. B. de novo methylation occurs in egg cells and maintenance methylation occurs in sperm cells. C. de novo methylation occurs in sperm and maintenance methylation occurs in somatic cells of offspring. D. de novo methylation occurs in egg cells and maintenance methylation occurs in somatic cells of offspring.

C

In one PCR cycle, the correct order of steps is A. primer annealing, primer extension, denaturation. B. primer annealing, denaturation, primer extension. C. denaturation, primer annealing, primer extension. D. denaturation, primer extension, primer annealing.

C

Insulators may exert their effect by A. acting as a barrier to changes in chromatin structure. B. blocking the effects of neighboring enhancers. C. both a and b. D. none of the above.

C

Let's suppose a researcher mixed together nucleotides with the following percentage of bases: 30% G, 30% C, and 40% A. If RNA was made via polynucleotide phosphorylase, what percentage of the codons would be 5´-GGC-3´? A. 30% B. 9% C. 2.7% D. 0%

C

One way that TNRE may occur involves the formation of that disrupts . A. a double-strand break, chromosome segregation B. an apurinic site, DNA replication C. a hairpin, DNA replication D. a free radical, DNA structure

C

Which of the following isnot an example of a spontaneous mutation? A. A mutation caused by an error in DNA replication B. A mutation caused by a tautomeric shift C. A mutation caused by UV light D. None of the above

C

Which of the following types of transposable elements involve an RNA intermediate? A. Insertion elements B. Simple transposons C. Retrotransposons D. All of the above

C

Which of these three mechanisms is most common in eukaryotic splicing? A. Group I: self splicing B. Group II: self splicing C. Pre-mRNA: splicing via a spliceosome D. All three are equally common

C

Which of the following may be used as a vector in a gene cloning experiment? A. mRNA B. Plasmid C. Virus D. Both b and c

D

Which of the following mechanisms can cause gene conversion? A. DNA mismatch repair B. DNA gap repair C. The resolution of a Holliday junction D. Both a and b

D

Which of the following would decrease mRNA stability? A. A longer polyA tail, which enhances the binding of polyA-binding protein B. A shorter polyA tail, which enhances the binding of polyA-binding protein C. A longer polyA tail, which inhibits the binding of polyA-binding protein D. A shorter polyA tail, which inhibits the binding of polyA-binding protein

D

With regard to a promoter, a transcriptional start site is A. located at the -35 position and recognized by σ factor. B. located at the -35 position and is where the first base is used as a template for RNA transcription. C. located at the +1 position and recognized by σ factor. D. located at the +1 position and is where the first base is used as a template for RNA transcription.

D

Which of the following are examples of epigenetic changes that alter gene expression? A. Chromatin remodeling B. Covalent histone modification C. Localization of histone variants D. DNA methylation E. Feedback loops F. All of the above

F

What type of bonding interactions cause the stem-loops to form?

Hydrogen bonding between complementary sequences causes the stem loops to form

Which of the following base sequences is/are used during transcription? A. Promoter and terminator B. Start and stop codons C. Ribosome-binding sequence D. Both a and b

a

An enzyme known as attaches an amino acid to the of a tRNA, thereby producing . A. aminoacyl-tRNA synthetase, anticodon, a charged tRNA B. aminoacyl-tRNA synthetase, 3´ single-stranded region of the acceptor stem, a charged tRNA C. polynucleotide phosphorylase, anticodon, a charged tRNA D. polynucleotide phosphorylase, anticodon, an aminoacyl tRNA

b

During attenuation, when tryptophan levels are high, the ________ stem-loop forms and transcription _________ the trpL gene. A. 2-3, ends just past B. 3-4, ends just past C. 1-2, continues beyond D. 3-4, continues beyond

b

The anticodon of a tRNA is located in the A. 3´ single-stranded region of the acceptor stem. B. loop of the first stem-loop. C. loop of the second stem-loop. D. loop of the third stem-loop.

c

What are the three roles of the 7-methulguanosine cap? A. proper splicing of pre-mRNA B. the exit of mRNA from the nucleus C. the binding of mRNA to a ribosome D. all of the above

d

Which of the following are examples of RNA modification? A. Splicing B. 7-methylguanosine cap C. PolyA tail D. All of the above

d

Which of the following is a function of the 7-methylguanosine cap? A. Exit of mRNA from the nucleus B. Efficient splicing of pre-mRNA C. Initiation of translation D. All of the above

d

In reverse transcriptase PCR, the starting biological material is A. chromosomal DNA. B. mRNA. C. proteins. D. all of the above.

B

Nitrous acid replaces amino groups with keto groups, a process called A. alkylation. B. deamination. C. depurination. D. crosslinking.

B

A mutation in one gene that reverses the effects of a mutation in a different gene is A. an intergenic suppressor. B. an intragenic suppressor. C. an up promoter mutation. D. a position effect.

A

According to the histone code hypothesis, the pattern of histone modifications acts like a language that A. influences chromatin structure. B. promotes transcriptional termination. C. inhibits the elongation of RNA polymerase. D. does all of the above.

A

An inborn error of metabolism is caused by A. a mutation in a gene that causes an enzyme to be inactive. B. a mutation in a gene that occurs in somatic cells. C. the consumption of foods that disrupt metabolic processes. D. all of the above.

A

For a riboswitch that controls transcription, the binding of a small molecule such as TPP controls whether the RNA A. has an antiterminator or terminator stem-loop. B. has a Shine-Dalgarno anti-sequestor or the Shine-Dalgarno sequence in a stem-loop. C. is degraded from its 5′ end. D. both a and b.

A

Homologous recombination refers to the exchange between DNA segments that are A. similar or identical in their DNA sequences. B. in close proximity to one another. C. broken due to ionizing radiation. D. misaligned along a chromosome.

A

In nucleotide excision repair in E. coli, the function of the UvrA/UvrB complex is to A. detect DNA damage. B. make cuts on both sides of the damage. C. remove the damaged piece of DNA. D. replace the damaged DNA with undamaged DNA.

A

In the Ames test, a ____________ number of colonies is observed if a substance ________ a mutagen, compared with the control that is not exposed to the suspected mutagen. A. significantly higher, is B. significantly higher, is not C. significantly lower, is D. significantly lower, is not

A

Sigma factor (σ) is needed during which stage(s) of transcription? A. Initiation B. Elongation C. Termination D. All of the above

A

The Kozak rules determine A. the choice of the start codon in complex eukaryotes. B. the choice of the start codon in bacteria. C. the site in the mRNA where translation ends. D. how fast the mRNA is translated.

A

The binding of iron regulatory protein (IRP) to the iron response element (IRE) in the 5′ region of the ferritin mRNA results in the A. inhibition of translation of the ferritin mRNA. B. stimulation of translation of the ferritin mRNA. C. degradation of the ferritin mRNA. D. both a and c.

A

The function of reverse transcriptase is to A. copy RNA into DNA. B. copy DNA into RNA. C. translate RNA into protein. D. translate DNA into protein.

A

What is the genetic code? A. The relationship between a three-base codon sequence and an amino acid B. The entire base sequence of an mRNA molecule C. The entire sequence from the promoter to the terminator of a gene D. The binding of tRNA to mRNA

A

When mice carrying the Avy allele exhibit a darker coat color, this phenotype is thought to be caused by dietary factors that result in A. a greater level of DNA methylation and a decrease in the expresssion of the Agouti gene. B. a lower level of DNA methylation and a decrease in the expresssion of the Agouti gene. C. a greater level of DNA methylation and the overexpresssion of the Agouti gene. D. a lower level of DNA methylation and the overexpression of the Agouti gene.

A

Which of the following conditions would cause transcription to be activated? A. A repressor plus an inducer B. A repressor plus a corepressor C. An activator plus an inhibitor D. None of the above

A

Combinatorial control refers to the phenomenon that A. transcription factors always combine with each other when regulating genes. B. the combination of several factors determines the expression of any given gene. C. small effector molecules and regulatory transcription factors are found in many different combinations. D. genes and regulatory transcription factors must combine with each other during gene regulation.

B

In the replica plating experiments of the Lederbergs, bacterial colonies appeared at the same locations in each of two secondary plates because A. T1 phage caused the mutations to happen. B. the mutations occurred on the master plate prior to T1 exposure and prior to replica plating. C. both a and b. D. none of the above.

B

In the triplet-binding assay of Nirenberg and Leder, an RNA triplet composed of three bases was able to cause the A. translation of a polypeptide. B. binding of a tRNA carrying the appropriate amino acid. C. termination of translation. D. release of the amino acid from the tRNA.

B

On its chromosome, an E. coli cell is lacI− lacZ+ lacY+ lacA+. It has an F′ factor that is lacI+ lacZ+ lacY+ lacA+. What is the expected level of expression of the lac operon genes (lacZ+ lacY+ lacA+) in the absence of lactose? A. Both lac operons would be expressed. B. Neither lac operon would be expressed. C. Only the chromosomal lac operon would be expressed. D. Only the lac operon on the F′ factor would be expressed.

B

The fourth codon in an mRNA-coding sequence is GGG, which specifies glycine. If we assume that no amino acids are removed from the polypeptide, which of the following statements is correct? A. The third amino acid from the N-terminus is glycine. B. The fourth amino acid from the N-terminus is glycine. C. The third amino acid from the C-terminus is glycine. D. The fourth amino acid from the C-terminus is glycine.

B

The process in which completely unmethylated DNA becomes methylated is called A. maintenance methylation. B. de novo methylation. C. primary methylation. D. demethylation.

B

The restriction enzymes used in gene-cloning experiments ___________, which generates sticky ends that can ___________. A. cut the DNA, enter bacterial cells B. cut the DNA, hydrogen bond with complementary sticky ends C. methylates DNA, enter bacterial cells D. methylates DNA, hydrogen bond with complementary sticky ends

B

What is an advantage of alternative splicing? A. Multiple genes can encode the same protein. B. The same gene can encode multiple proteins. C. The same protein can be digested in multiple ways. D. All of the above

B

What is an operon? A. A site in the DNA where a regulatory protein binds B. A group of genes under the control of a single promoter C. An mRNA that encodes several genes D. All of the above

B

Which RNA polymerase in eukaryotes is responsible for the transcription of genes that encode proteins? A. RNA polymerase I B. RNA polymerase II C. RNA polymerase III D. All of the above

B

Which of the following characteristics is typical of a eukaryotic gene that can be transcribed? A. The core promoter is wrapped around a nucleosome. B. The core promoter is found in a nucleosome-free region. C. The terminator is wrapped around a nucleosome. D. None of the above are correct.

B

With regard to transcriptional termination in eukaryotes, which model suggests that RNA polymerase is physically removed from the DNA by an exonuclease? A. Allosteric model B. Torpedo model C. Both models D. Neither model

B

The function of photolyase is to repair A. double-strand breaks. B. apurinic sites. C. thymine dimers. D. all of the above.

C

The reason why Beadle and Tatum observed four different categories of mutants that could not grow on media without methionine is because A. the enzyme involved in methionine biosynthesis is composed of four different subunits. B. the enzyme involved in methionine biosynthesis is present in four copies in the Neurospora genome. C. four different enzymes are involved in a pathway for methionine biosynthesis. D. a lack of methionine biosynthesis can inhibit Neurospora growth in four different ways.

C

The three stages of transcription are A. initiation, ribosome-binding, and termination. B. elongation, ribosome-binding, and termination. C. initiation, elongation, and termination. D. initiation, regulation, termination.

C

Which of the following is the proper order of steps in a gene-cloning experiment involving vectors? 1. Add DNA ligase. 2. Incubate the chromosomal DNA and the vector DNA with a restriction enzyme. 3. Introduce the DNA into living cells. 4. Mix the chromosomal DNA and vector DNA together. A. 1, 2, 3, 4 B. 2, 3, 1, 4 C. 2, 4, 1, 3 D. 1, 2, 4, 3

C

A chromatin-remodeling complex may A. change the locations of nucleosomes. B. evict nucleosomes from DNA. C. replace standard histones with histone variants. D. do all of the above.

D

A point mutation could be caused by A. depurination. B. deamination. C. tautomeric shift. D. all of the above.

D

An example of a posttranslational covalent modification that may regulate protein function is A. phosphorylation. B. acetylation. C. methylation. D. all of the above.

D

Antibody diversity is produced by A. V(D)J recombination. B. imprecise end joining during V(D)J recombination. C. somatic hypermutation. D. all of the above.

D

Double-strand breaks can be repaired by A. homologous recombination repair (HRR). B. nonhomologous end joining (NHEJ). C. nucleotide excision repair (NER). D. both a and b.

D

During real-time PCR, the synthesis of PCR products is analyzed A. at the very end of the reaction by gel electrophoresis. B. at the very end of the reaction by fluorescence that is emitted within the thermocycler. C. during the PCR cycles by gel electrophoresis. D. during the PCR cycles by fluorescence that is emitted within the thermocycler.

D

During the initiation stage of translation in bacteria, which of the following event(s) occurs? A. IF1 and IF3 bind to the 30S subunit. B. The mRNA binds to the 30S subunit and tRNAfMet binds to the start codon in the mRNA. C. IF2 hydrolyzes its GTP and is released; the 50S subunit binds to the 30S subunit. D. All of the above events occur.

D

During the molecular process of homologous recombination between homologous chromosomes, A. Holliday junction forms. B. branch migration occurs. C. a heteroduplex region forms. D. all of the above occur.

D

Each ribosomal subunit is composed of A. multiple proteins. B. rRNA. C. tRNA. D. both a and b.

D

How can methylation affect transcription? A. It may prevent the binding of regulatory transcription factors. B. It may enhance the binding of regulatory transcription factors. C. It may attract the binding of methyl-CpG-binding proteins, which inhibit transcription. D. All of the above are possible.

D

In the splicing process, snRNPs are responsible for A. recognizing the intron boundaries B. cutting out the intron C. connecting the two adjacent exons together D. all of the above

D

Regulatory transcription factors can be modulated by A. the binding of small effector molecules. B. protein-protein interactions. C. covalent modifications. D. all of the above.

D

The binding of _________ to the lac repressor causes the lac repressor to _________ to the operator site and thereby _________ transcription. A. glucose, bind, inhibits B. allolactose, bind, inhibits C. glucose, not bind, increases D. allolactose, not bind, increases

D

The function of transposase is A. to recognize inverted repeats. B. to remove a TE from its original site. C. to insert a TE into a new site. D. all of the above.

D

The process of RNA interference may lead to A. the degradation of an mRNA. B. the inhibition of translation of an mRNA. C. the synthesis of an mRNA. D. both a and b.

D

The reading frame begins with a and is read . A. promoter, one base at a time B. promoter, in groups of three bases C. start codon, one base at a time D. start codon, in groups of three bases

D

The site(s) on a ribosome where tRNA molecules may be located include the A. A site. B. P site. C. E site. D. all of the above.

D

Transcription of protein-encoding genes in eukaryotes requires A. five general transcription factors. B. RNA polymerase II. C. a DNA sequence containing a TATA box and transcriptional start site. D. all of the above.

D

Transcriptional activation of eukaryotic genes involves which of the following events? A. Changes in nucleosome locations B. Changes in histone composition within nucleosomes C. Changes in histone modifications D. All of the above

D

Translation can be regulated by A. translational repressors. B. antisense RNA. C. attenuation. D. both a and b.

D

When an E. coli cell is exposed to glucose, how does this affect the regulation of the lac operon via CAP? A. cAMP binds to CAP and transcription is increased. B. cAMP binds to CAP and transcription is decreased. C. cAMP does not bind to CAP and transcription is increased. D. cAMP does not bind to CAP and transcription is decreased.

D

Which of the following DNA repair systems may involve the removal of a segment of a DNA strand? A. Base excision repair B. Nucleotide excision repair C. Mismatch repair D. All of the above

D

Which of the following is an example of a somatic mutation? A. A mutation in an embryonic muscle cell B. A mutation in a sperm cell C. A mutation in an adult nerve cell D. Both a and c.

D

Which of the following is not a key difference between bacteria and eukaryotes? A. Initiation of transcription requires more proteins in eukaryotes. B. A 7-methylguanosine cap is added only to eukaryotic mRNAs. C. Splicing is common in complex eukaryotes but not in bacteria. D. All of the above are key differences.

D

Operons involved with the biosynthesis of molecules, such as amino acids, are most likely to be regulated in the following manner: A. The product of the biosynthetic pathway represses transcription. B. The product of the biosynthetic pathway activates transcription. C. A precursor of the biosynthetic pathway represses transcription. D. A precursor of the biosynthetic pathway activates transcription.

a

When tryptophan binds to the trp repressor, this causes the trp repressor to __________ to the trp operator and ________ transcription. A. bind, inhibit B. not bind, inhibit C. bind, activate D. not bind, activate

a

If a tRNA has an anticodon with the sequence 5´-CAG-3´, which amino acid does it carry? A. Aspartic acid B. Leucine C. Valine D. Glutamine

b

Which of the following statements about the spliceosome is false? A. A spliceosome splices pre-mRNA molecules. B. A spliceosome removes exons from RNA molecules. C. A spliceosome is composed of snRNPs. D. A spliceosome recognizes the exon-intron boundaries and the branch site.

b

A ribozyme is A. a complex between RNA and a protein. B. an RNA that encodes a protein that functions as an enzyme. C. an RNA molecule with catalytic function. D. a protein that degrades RNA molecules.

c

A type of secondary structure found in proteins is A. an α helix. B. a β sheet. C. both a and b. D. none of the above.

c