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 can only create a new strand of DNA from the 5’ to 3’ end
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DNA helicase sometimes breaks the DNA
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Newly formed DNA tends to break apart easily into fragments
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DNA polymerase can only create a new strand of DNA from the 3’ to 5’ end
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Detailed explanation-1: -DNA synthesis occurs only in the 5’ to 3’ direction. On the leading strand, DNA synthesis occurs continuously. On the lagging strand, DNA synthesis restarts many times as the helix unwinds, resulting in many short fragments called “Okazaki fragments.”
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: -One strand at the replication fork is continuously synthesised in the 5′ to 3′ direction (leading strand) while the (lagging strand) second strand is discontinuously synthesised in the 3′ to 5′ direction in short fragments which are referred to as the Okazaki fragments.
Detailed explanation-4: -In prokaryotic cells, polymerase III is the major replicative polymerase, functioning in the synthesis both of the leading strand of DNA and of Okazaki fragments by the extension of RNA primers.
Detailed explanation-5: -A new DNA strand only grows in the 5’ to 3’ direction because the enzyme that adds new bases to a growing strand requires a free 3’ OH group. The sugar-phosphate backbone of DNA is made up of phosphodiester linkages between 3’ OH groups and 5’ phosphate groups.