THE MOLECULAR BASIS OF INHERITANCE
DNA MAKES RNA MAKES PROTEIN
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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5’
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3’
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both 3’ and 5’
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the end with the phosphate
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Detailed explanation-1: -DNA polymerase enzymes cannot begin a new polynucleotide chain by linking two nucleoside triphosphates together. Instead, they absolutely require a base-paired 3′-OH end of a primer strand on which to add further nucleotides (see Figure 5-4).
Detailed explanation-2: -After a primer is synthesized on a strand of DNA and the DNA strands unwind, synthesis and elongation can proceed in only one direction. As previously mentioned, DNA polymerase can only add to the 3’ end, so the 5’ end of the primer remains unaltered.
Detailed explanation-3: -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.)
Detailed explanation-4: -DNA replication goes in the 5’ to 3’ direction because DNA polymerase acts on the 3’-OH of the existing strand for adding free nucleotides.
Detailed explanation-5: -A DNA strand with the fifth carbon within the sugar ring at its terminus is said to have a five prime end. On the 3′ carbon of its terminal sugar, the 3′ end has a free hydroxyl group. The three prime ends of a molecule is the end that ends in a 3′ phosphate group.