Quiz 17: DNA Replication,repair,and Recombination

The DNA polymerase reaction occurs in the ________ as incoming nucleotides are added to ________ end(s)of the growing DNA chain. A)5' → 3' direction; the 3'-hydroxyl B)5' → 3' direction; the 3'-phosphate C)3' → 5' direction; the 5'-hydroxyl D)3' → 5' direction; the 5'-phosphate E)5' → 3' direction or 3' → 5' direction; both

The energy needed to polymerize DNA is supplied by A)the hydrolysis of the phosphate bonds of ATP by an accessory protein that is part of the DNA polymerase holoenzyme. B)the hydrolysis of the phosphate bonds of ATP or GTP,depending on the form of DNA polymerase. C)the hydrolysis of the phosphate bonds of the deoxynucleoside triphosphates that are being added to the new DNA chain. D)the formation of the covalent bond between the phosphate of the nucleoside and the hydroxyl group. E)the hydrolysis of the RNA primers used in DNA replication.

In DNA replication,the leading strand of DNA ________,while the other newly forming strand,called the lagging strand,________. A)is synthesized in the 5' → 3' direction; the new DNA is synthesized in the 3' → 5' direction B)is synthesized in the 3' → 5' direction; the new DNA is synthesized in the 5' → 3' direction C)does not require an RNA primer; an RNA primer is required D)is synthesized as a continuous chain; the new DNA is formed in a series of short,discontinuous fragments E)is synthesized in a series of short,discontinuous fragments; the new DNA is synthesized as a continuous chain

The most common form of spontaneous replication error is A)tautomeric shift. B)double-stranded DNA breaks. C)thymine dimer addition. D)base analogue addition. E)DNA intercalation.

Strand slippage results in ________,which can cause a number of human diseases such as fragile X syndrome. A)tautomeric shift B)double-stranded DNA breaks C)pyrimidine dimer addition D)deletion of large sections of DNA E)the re-replication of highly repetitive DNA sequences

DNA replication is A)conservative. B)dispersive. C)semiconservative. D)irregular. E)None of these selections apply.

Which of the following do not undergo theta replication? A)bacterial genomes B)mitochondrial genomes C)chloroplast genomes D)plasmids E)protist genomes

DNA replication A)requires a type of RNA polymerase. B)is partially regulated by promoter/terminator sites. C)proceeds by making two continuous strands. D)is not edited once polymerization has occurred. E)is conservative.

Each of the following are associated with replicons except A)origin of replication. B)terminator sites. C)initiator proteins. D)minichromosome maintenance proteins. E)helicase loaders.

A NASA probe returned samples of rocks from the surface of Mars.From these rocks,a prokaryotic organism was isolated and remained viable under conditions similar to those of Mars.The organisms are capable of dividing to replicate themselves.In order to determine whether the DNA replication of these organisms was semiconservative,an experiment using N15/N14 (similar to that of Meselson and Stahl)was performed.If the method of DNA replication were conservative,after one generation one would expect to see A)all of the DNA in the heavy (N¹⁵)band. B)all of the DNA in the light (N¹⁴)band. C)all of the DNA at a point midway between the heavy and light bands. D)half of the DNA in the light band,the other half in the heavy band. E)None of these are correct.

An isolate of a mutant bacterium appears to grow more slowly than the wild-type population from which it was isolated.Further studies showed that the slower growth was due to a markedly reduced DNA polymerase I activity.From this information,one would expect that this organism would also be deficient in the activity of DNA A)excision repair. B)recombination. C)transcription. D)translation. E)unwinding.

Spontaneous hydrolysis reactions between DNA and surrounding water molecules commonly cause A)pyrimidine dimer formation. B)depurination. C)tautomeric shift. D)double-stranded DNA breaks. E)deletion mutations.

Deamination is a spontaneous DNA mutation that converts cytosine to A)thymine. B)guanine. C)adenine. D)uracil. E)None of these are correct.

Thymine is used in DNA despite the fact that it is energetically more expensive to synthesize than uracil because A)spontaneous deamination reactions convert cytosine to uracil at a fairly high rate. B)uracil is more sensitive to ultraviolet (UV)damage. C)uracil is more susceptible to depurination. D)uracil can only bind with ribose,not deoxyribose. E)thymine is less likely to undergo spontaneous deamination than uracil.

Ultraviolet (UV)light-treated bacteria would have increased DNA damage in the form of A)analog incorporation. B)pyrimidine dimer formation. C)intercalation of the bases. D)direct transition of the bases. E)deamination.

DNA damage can occur A)due to exposure to certain chemicals or radiation. B)spontaneously. C)during DNA replication. D)during transcription. E)during DNA replication,spontaneously,or due to exposure to certain chemicals or radiation.

Base-modifying chemicals such as aflatoxin B₁ or nitrosoguanidine cause mutations by A)increasing the likelihood of depurination. B)causing double-stranded breaks in the DNA sugar-phosphate backbone. C)causing mispairing during DNA replication. D)causing pyrimidine dimers. E)increasing the likelihood of depurination or causing mispairing during DNA replication.

Insertion and deletion mutations can be caused by A)spontaneous hydrolysis reactions between DNA and water. B)intercalating agents. C)the addition of DNA adducts. D)tautomeric shift. E)spontaneous hydrolysis reactions between DNA and water or the addition of DNA adducts.

DNA repair in eukaryotes and prokaryotes A)relies on DNA polymerases to correct all mutations. B)relies on completely different mechanisms. C)is accomplished by multiple specialized pathways. D)can only repair abnormal nucleotides such as pyridine dimers and depurinated bases. E)is very ineffective.

Which of the following proteins is observed exclusively in association with prokaryotic DNA replication? A)DNA polymerase I B)primase C)helicase D)single-strand binding proteins E)telomerase

Which of the following eukaryotic DNA polymerases replicates mitochondrial DNA? A)alpha B)beta C)delta D)epsilon E)gamma

Which of the following proteins is observed exclusively in association with eukaryotic DNA replication? A)DNA polymerase I B)DNA gyrase C)single-strand binding proteins D)DNA ligase E)telomerase

Base excision repair is used to A)correct base mismatches in newly synthesize DNA. B)fix double-strand DNA breaks. C)remove intercalating agents. D)remove modified or depurinated bases. E)remove intercalating agents and modified or depurinated bases.

Nonhomologous end joining is used to A)correct base mismatches in newly synthesized DNA. B)fix double-strand DNA breaks. C)avoid deletion or insertion of bases. D)remove modified or depurinated bases. E)avoid deletion or insertion of bases and remove modified or depurinated bases.

A 40-year-old patient has been diagnosed with cancer.Sequencing of cancer cell genomes reveals a high frequency of G/C to A/T base pairs conversion.The DNA repair system that is most likely deficient in this patient is the A)base excision repair pathway. B)SOS repair pathway. C)nonhomologous end-joining pathway. D)nucleotide excision repair pathway. E)synthesis-dependent strand annealing pathway.

Cells that are very sensitive to UV radiation most likely have a defect in the A)base excision repair pathway. B)SOS repair pathway. C)nonhomologous end-joining pathway. D)nucleotide excision repair pathway. E)synthesis-dependent strand annealing pathway.

In hereditary nonpolyposis colon cancer,mutations in MutS and MutH proteins result in the accumulation of mutations caused by A)mismatched base pairs. B)structurally damaged bases. C)double-stranded DNA breaks. D)thymine dimers. E)DNA recombination.

Which of the following is involved in proofreading during DNA replication? A)5' to 3' exonuclease activity of DNA polymerase B)3' to 5' exonuclease activity of DNA polymerase C)5' to 3' endonuclease activity of DNA polymerase D)3' to 5' endonuclease activity of DNA polymerase E)RNA polymerase

Multiple sites of DNA replication along eukaryotic chromosomes are known as A)replicons. B)multireplication forks. C)helicase loaders. D)ARS elements. E)None of these answers are correct.

The protein(s)that facilitate the unfolding of chromatin fibers ahead of the replication fork is (are) A)helicase. B)scaffold proteins. C)chromatin remodeling proteins. D)replisomal proteins. E)helicase and scaffold proteins.

Which of the following DNA repair mechanisms is most prone to error? A)mismatch repair B)base excision repair C)SOS repair D)nucleotide excision repair E)All DNA repair systems are equally prone to error.

Double-stranded break repair mechanisms A)are error prone. B)may join nonhomologous ends of DNA together. C)are part of the SOS repair system. D)may use homologous DNA to repair the damage. E)are error prone and may join nonhomologous ends of DNA together or use homologous DNA to repair the damage.

Homologous recombination may result in gene conversion when used to fix double-stranded DNA breaks because A)sister chromatids are always identical. B)homologous recombination is prone to errors,potentially causing permanent genetic mutations. C)strand invasion may introduce new genes onto the damaged chromosome. D)homologous chromosomes may carry different alleles of the same gene. E)the Holliday junction may migrate,resulting in loss of genetic material.

Transposase is A)required to resolve a Holliday junction. B)involved in the movement of mobile genetic elements in prokaryotic and eukaryotic genomes. C)found only in prokaryotic transposons. D)required for synthesis-dependent strand annealing to repair double-stranded DNA breaks. E)necessary for replicative transposition but not conservative transposition.

It has been observed that when plants are subjected to extreme physical stress such as drought or high salinity,the transcription and activity of transposase genes increases.Increased transposase activity may A)increase the rate of mutation under stressful conditions. B)aid in repairing DNA damage caused by stressful conditions. C)halt DNA replication and cell division. D)increase homologous recombination and genetic diversity. E)explain why some plants can't withstand drought conditions.

Composite transposons are composed of A)the transposase gene flanked by inverted repeat sequences. B)a mobile gene flanked by inverted repeat sequences. C)the transposase gene only. D)several genes,such as antibiotic resistance genes,flanked by transposase genes. E)several genes,including transposase,flanked by inverted repeat sequences.

Small pieces of DNA synthesized on the lagging strand are called ________.

The type of DNA repair that fixes mistakes in nucleotide incorporation after DNA replication is known as ________ repair.

A way of making multiple copies of a segment of DNA from a single template (without culturing cells)is known as ________.

Linear chromosomes have multiple sites of DNA replication known as ________.

Telomerases are important in the complete replication of linear chromosomes because there is no ________ at the ends of the lagging strands.

________ synthesis is a damage-tolerant mechanism that allows synthesis of a new DNA strand from a damaged template.

The ________ pathway uses a set of proteins that bind to ends of two broken DNA fragments and join them together.

________ are mobile genetic elements discovered in corn by Barbara McClintock.

The mechanism that allows chromatin exchange during meiosis in eukaryotes is ________.

Bypass polymerases that are more tolerant of DNA damage and can continue DNA synthesis at damaged sites produce a daughter strand that contains ________.

The inherited disorder xeroderma pigmentosum causes extreme sensitivity to the sun because of defects in the ________ pathway.

At least one aspect of aging has been determined to be the shortening of ________ with each successive round of DNA replication.

Several human disorders are caused by DNA repair pathway deficiencies.Choose one and describe: (1)what the deficiency is and (2)how the defect affects people with the disease.

DNA contains thymine rather than uracil.Why is the presence of thymine in DNA advantageous? What effect would the presence of uracil in DNA have on DNA repair?

Why do eukaryotic chromosomes have multiple origins of replication? Design an experiment that allows you to test your hypothesis.

Using specific examples,distinguish between those mutations that are spontaneous and those that are the result of exposure to substances or radiation.How might some of the mutagenic substances be used in cellular biology and medicine?

Compare and contrast nonhomologous end joining (NHEJ)and homologous recombination as methods of repairing double-stranded breaks in DNA.Under what conditions or in what organisms is homologous recombination not a likely mechanism for repair of double-stranded breaks?