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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3’; hydrogen attached to the 2’ carbon indicating that it is deoxyribose not ribose.
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5’; hydrogen attached to the 2’ carbon indicating that it is deoxyribose not ribose.
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5’; hydroxyl attached to the 3’ carbon to be used in the formation of the phosphodiester bond (covalent).
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3’; hydroxyl attached to the 3’ carbon to be used in the formation of the phosphodiester bond (covalent).
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Detailed explanation-1: -As new nucleotides are added to a strand of DNA or RNA, the strand grows at its 3’ end, with the 5′ phosphate of an incoming nucleotide attaching to the hydroxyl group at the 3’ end of the chain. This makes a chain with each sugar joined to its neighbors by a set of bonds called a phosphodiester linkage.
Detailed explanation-2: -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-3: -DNA is always synthesized in the 5’-to-3’ direction, meaning that nucleotides are added only to the 3’ end of the growing strand.
Detailed explanation-4: -Primers and primase DNA polymerases can only add nucleotides to the 3’ end of an existing DNA strand. (They use the free-OH group found at the 3’ end as a “hook, ” adding a nucleotide to this group in the polymerization reaction.)