26. Which of the following statements about DNA ligation is FALSE? A. For enzyma

Question

26. Which of the following statements about DNA ligation is FALSE?

A. For enzymatic ligation of two adjacent single strands of DNA, a complementary strand that spans the two ligating strands is required.

B. T4 DNA ligase with phosphoramide-linked AMP attacks the 3'hydroxyl at the nick in two DNA strands undergoing ligation.

C. Hydrogen ions (H+) are a side product of T4 DNA ligase function.

D. T4 DNA ligase completes DNA ligation by catalysing the joining of the 3' OH and the 5' phosphate groups at a nick.

E. T4 DNA ligase can join blunt-ended fragments.

27. Which of the following statements about genomes is NOT true?

A. genomes vary widely in size from species to species

B. genomes vary widely in information content

C. functional parts of genome are more highly conserved (sequence-wise) than non-functional parts

D. prokaryotic genomes are mostly non-functional whereas, eukaryotic genomes are mostly functional

E. chromosomes are information organelles

28. How do modified and unmodified histone subunits become distributed among nucleosomes following replication?

A. The newly synthesized DNA strand contains unmodified histone subunits, while the old strand retains the modified histones.

B. Both strands of DNA are repopulated first with a mixture of modified and unmodified H2A histones, followed by mixtures of H2B, H3, and, finally, H4.

C. Both strands of DNA are repopulated first with a mixture of modified and unmodified H2A and H2B histones, followed by mixtures of H3 and finally mixtures of H4.

D. Both strands of DNA retain H3-H4 modified pairs, and then are repopulated with unmodified H3-H4 pairs, followed by modified and unmodified H2A-H2B.

E. Both strands of DNA retain H2A-H2B modified pairs, and are then repopulated with unmodified H2A-H2B pairs, followed by modified and unmodified H3-H4 pairs.

37. When a replication error is detected:

A. the mispaired nucleotide is removed by a condensation reaction, releasing a water.

B. the mispaired 3' terminus frays by four nucleotides to allow it to be inserted into the 3-5' exonuclease site.

C. the —OH group on a tyrosine acts as a nucleophile to remove the incorrect base.

D. the 5'-3' exonuclease site uses acidic amino acids to catalyze nucleotide removal.

E. all of the above are correct.

38. The clamp loader loads the ß sliding clamp onto the DNA. Review the steps listed below.

Which step would come SECOND?

A. ATP binds to the y (gamma) subunits, which undergo a conformation change.

B. Double-stranded DNA passes through the 13 clamp.

C. The y (gamma) — ß clamp — ATP complex binds primed DNA.

D. y (gamma) subunits bind to and open the clamp.

E. Single-stranded DNA passes through the side of the clamp loader gap.

Explanation / Answer

26.Correct answer is:C. Hydrogen ions (H+) are a side product of T4 DNA ligase function.

27.Correct answer is:D. prokaryotic genomes are mostly non-functional whereas, eukaryotic genomes are mostly functional

28.Correct answer is : D.Both strands of DNA retain H3-H4 modified pairs, and then are repopulated with unmodified H3-H4 pairs, followed by modified and unmodified H2A-H2B.

37.Correct answer is:B.the mispaired 3' terminus frays by four nucleotides to allow it to be inserted into the 3-5' exonuclease site

38.Correct answer is:E: Single-stranded DNA passes through the side of the clamp loader gap.

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