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单选题 Part of the triplet genetic code involving mRNA codon triplets that start with U is shown below. Using the portion of the genetic code shown, which of the following mutations in the 3' to 5' DNA template segments corresponds to a nonsense mutation?
学科：2023生物化学
时间：2023-11-03 03:05:16
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题目1单选题
why mammalian genomes are 100 times the size of bacterial genomes yet are replicated in just a few minutes. Which of the following best explains this factA. Eukaryotic DNA polymerases are extraordinarily fast compared with prokaryotic polymerasesB. The higher temperature of mammalian cells allows for an exponentially higher replication rateC. The presence of histones in mammalian chromatin speeds up the rate of DNA replicationD. Histones and microRNAs complexed with bacterial DNA speed up the rate of DNA replicationE. Hundreds of replication forks work simultaneously on each piece of mammalian genomic DNA
题目2单选题
A 2-year-old child presents with poor weight gain, sparse hair, unusual face with sunken eyes, and skin that reddens markedly in sunlight. A diagnosis of Cockayne syndrome (MIM*216400) is considered and studies of DNA synthesis are undertaken. In vitro assay of labeled thymidine incorporation reveals decreased levels of DNA synthesis compared to controls, but normal-sized labeled DNA fragments. The addition of protein extract from normal cells gently heated to inactivate DNA polymerase restores DNA synthesis in Cockayne cells to normal. Which of the following enzymes used in DNA replication is most likely to be defective in Cockayne syndromeA. Unwinding proteinsB. DNA-directed RNA polymeraseC. DNA polymerase ID. DNA ligaseE. DNA-directed DNA polymerase
题目3单选题
Part of the triplet genetic code involving mRNA codon triplets that start with U is shown below. Using the portion of the genetic code shown, which of the following mutations in the 3' to 5' DNA template segments corresponds to a nonsense mutation?<img src="https://tihai-oss-cloud.itihey.com/img/b16b4875cb76c3cd5a77b41c5dd6ca01.jpg">A. ACGACGACG to ACAAACACGB. AGAATAACA to AAAATAACAC. AACAACAAC to AACAAGAACD. AAAATGAGC to AAAATAAGCE. AGGAATATG to AGGAATATT
题目4单选题
Replication of DNA starts with the unwinding of the entire DNA molecule. Each original strand is a therefore a template from which a new strand is synthesized based on complementary base pairing by DNA polymerase. The new DNA consists of an old parent strand and a new daughter strand. This process is calledA. Hydrolytic cleavageB. Helical pairingC. Semiconservative replicationD. Heredity
题目5单选题
DNA replication results inA. Protein productionB. Two new daughter strandsC. Heavy DNAD. Induced mutationsE. mRNA transcripts
题目6单选题
DNA replication is semiconservative. Why do you think this is trueA. Requires less energy B、C、 D、B. Only one DNA strand can be copied at a timeC. Increased fidelityD. DNA replication starts at specific sites onlyE. RNA primer limitations
题目7单选题
Why does lagging strand synthesis consist of discontinuous Okazaki fragmentsA. A、There is a shortage of dNTPs for lagging strand synthesisB. Okazaki fragments are riddled with mistakes; proofreading enzymes chop up the nucleotide into short fragmentsC. Lagging strand DNA polymerase can only handle a few nucleotides at a timeD. DNA is synthesized 5' to 3'. Replication can only proceed from the unwound portion of DNA outward
题目8单选题
Single-stranded binding proteins (SSB) bind to the outer backbone of DNA during replication. What would you predict about SSBsA. They contain arginine and lysine residuesB. They hydrolyze phosphodiester bondsC. Sequence-specific bindingD. They form covalent bonds to sugars
题目9单选题
Telomerase contains a ribozymeA. Telomerase contains a ribozymeB. Telomerase adds a repeating sequence to the 5' end of DNAC. Telomerase activity decreases as the cell agesD. Telomerase adds a repeating sequence to the 3' end of DNAE. Telomerase is found only in eukaryotes
题目10单选题
DNA replication is not perfect; a mistake is made for every 104 to 105 nucleotides added. However, there are proofreading enzymes that excise incorrect bases and insert the correct one. Which of the following enzymes proofread DNAA. DNA ligaseB. DNA gyraseC. DNA IID. TopoisomeraseE. DNA Polymerase I and III
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