DNA Structure and Replication

ID #2084

When the RNA primer is added in DNA replication, why is this not considered synthesis of RNA? Is it because the RNA nucleotides are not binding to each other? Or is it just that the first nucleotide that is part of the primer is hybridized to the DNA strand, so it doesnt require energy, but then the RNA nucleotides that are added after that do have their pyrophosphate hydrolyzed for energy, because they need to covalenty bind to the previous RNA nucleotide? Or do the RNA nucleotides not bind to each other, but only hybridize to the DNA strand, and therefore do not require any covalent bonding or energy?


Yes, you answered your own first question. Incorporation of the first nucleotide is just a hybridization, not a synthesis reaction, but each subsequent base added is in fact a synthesis.

 

    And when DNA polymerase 1 replaces the RNA primer with DNA, isn't the first DNA nucleotide that is added to replace the RNA, not going to have a free 3' OH group to bind to?

 

Actually, it gets that 3'OH group from the last base added by DNA polymerase III in the next Okazaki fragment. That's why the "clean up" comes later, to give the next fragment time to form.

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