GENETICS AND EVOLUTION
MOLECULAR BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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5’ end ____ 3’ end
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3’ end ____ 5’ end
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3’ end ____ 3’ end
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sugar group ____ phosphate group
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Detailed explanation-1: -DNA polymerase I (pol I) processes RNA primers during lagging-strand synthesis and fills small gaps during DNA repair reactions.
Detailed explanation-2: -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-3: -The telomerase attaches to the end of the chromosome, and complementary bases to the RNA template are added on the end of the DNA strand. Once the lagging strand template is sufficiently elongated, DNA polymerase can now add nucleotides that are complementary to the ends of the chromosomes.
Detailed explanation-4: -DNA is always synthesized in the 5’-to-3’ direction, meaning that nucleotides are added only to the 3’ end of the growing strand. As shown in Figure 2, the 5’-phosphate group of the new nucleotide binds to the 3’-OH group of the last nucleotide of the growing strand.