THE MOLECULAR BASIS OF INHERITANCE
DNA REPLICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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DNA polymerase III can only add nucleotides in the 5’
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DNA polymerase III can only add nucleotides in the 3’
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RNA polymerase can only add nucleotides in the 5’
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single strand binding proteins only work on one strand
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Detailed explanation-1: -DNA is always synthesized in the 5’ to 3’ direction because DNA polymerases can only catalyze phosphodiester bond formation (a condensation reaction) between the 3’ OH of the sugar of the last nucleotide of an existing strand and the 5’ phosphate group of the incoming nucleotide.
Detailed explanation-2: -These fragments are formed on the lagging strand for the synthesis of DNA. The direction is 5’ to 3’ toward the replication fork. These fragments make the replication of only one of the two strands possible hence increasing the efficiency of replication.
Detailed explanation-3: -Nucleotides cannot be added to the phosphate (5’) end because DNA polymerase can only add DNA nucleotides in a 5’ to 3’ direction. The lagging strand is therefore synthesised in fragments. The fragments are then sealed together by an enzyme called ligase.
Detailed explanation-4: -Okazaki fragments are short sections of DNA formed at the time of discontinuous synthesis of the lagging strand during replication of DNA. It is essential as it allows for the synthesis of both the daughter strands required for cell division.