A new DNA strand elongates only in the 5\' to 3\' direction because A) DNA polym

Question

A new DNA strand elongates only in the 5' to 3' direction because A) DNA polymerase can only add nucleotides to the free 3' end. B) DNA polymerase begins adding nucleotides at the 5' end of the template. C) replication must progress toward the replication fork. D) Okazaki fragments prevent elongation in the 3' to 5' direction. What is the function of topoisomerase? A) stabilizing single-stranded DNA at the replication fork. B) adding methyl groups to bases of DNA C) relieving strain in the DNA ahead of the replication fork. D) unwinding of the double helix E) elongating new DNA at a replication fork by adding nucleotides to the existing chain What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? A) It synthesizes RNA nucleotides to make a primer. B) It catalyzes the lengthening of telomeres. C) It unwinds the parental double helix. D) It stabilizes the unwound parental DNA. E) It joins Okazaki fragments together. Which of the following help(s) to hold the DNA strands apart while they are being replicated? A) primase B) ligase C) single-strand binding proteins D) nuclease E) DNA polymerase During DNA replication, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments? A) helicase B) DNA polymerase III C) ligase D) DNA polymerase I E) primase During DNA replication, which of the following enzymes separates the DNA strands during replication? A) helicase B) DNA polymerase III C) liase D) DNA polymerase I E) primase During DNA replication, which of the following enzymes covalently connects segments of DNA? A) helicase B) DNA polymerase C) ligase D) DNA polymerase I E) primase

Explanation / Answer

[ I am anwering question 21-24. I hope this helps. Thanks ]

1. The leading strand is synthesized with twice rate as compared to the lagging strand. The DNA polymerase cannot add new nucleotide at 5' end, it rather adds new nucleotide at free 3' end. Hence, the DNA strand elongates at 5'-->3' direction. The correct answer is option A.

2. Topoisomerases are the enzymes that helps in DNA unwinding or overwinding. During DNA replication, the DNA strands becomes overwind ahead of replication fork, in this case topoisomerase helps. The correct answer is option C.

3. The DNA ligase is a ligation enzyme. Its function in DNA replication is to join the okazaki fragments to form a continuous chain of DNA. The correct answer is option E.

4. Single stranded binding protein is a type of protein that binds to single-stranded regions of DNA. The correct answer is option C.

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