DNA: Structure and Replication - 10•DNA Polymerase and the Single Chain TemplateDNA polymerase's inability to add nucleotides to a single chain is solved bystarting replication with a RNA primer activated by an enzyme calledprimase. Primase catalyzes a short RNA molecule or primer that is used tostart the synthesis of DNA.Once the DNA strand has been "primed" by primase adding the RNA primer,DNA polymerase can go to work adding nucleotides to the available 3' carbonof the growing molecule. (This is sometimes called the free sugar end of theDNA molecule. The opposite end 5' carbon of the nucleotide's sugar thatbonds to the phosphate is called the free phosphate end.) DNA polymerasewill also eventually replace the RNA nucleotides of the primer with DNAnucleotides.•DNA and the Anti-parallel Template StrandsFor DNA's second limitation, DNA polymerase can only attach a nucleotide tothe exposed -OH group on the 3' end of the sugar on the template. DNA isalways synthesized in the 5' ±
This is the end of the preview.
access the rest of the document.