Which enzyme replaces RNA primers with DNA after elongation a. DNA polymerase I
ID: 9217 • Letter: W
Question
Which enzyme replaces RNA primers with DNA after elongationa. DNA polymerase I
b. DNA polymerase III
c. RNA polymerase I
d. RNA primase
e. DNA ligase
Explain please!
Explanation / Answer
(I assume that this is in DNA replication, if not then disregard) A. DNA Polymerase I Alright, so the process of DNA replication starts off with DNA being double stranded. The cell needs to split the DNA for it to be replicated so and enzyme named Helicase comes in and breaks the double bonds between the nitrogenous bases (A,T,C,G). As Helicase is splitting the DNA molecule another enzyme just in front of Helicase (and the replication fork) is releasing the tension in the DNA that is being formed by it being unwound, this enzyme is Topoisomerase. Once the DNA has been split it needs to be held open until it is replicated so Single Stranded Binding Proteins attach to the free nucleotides preventing the DNA from snapping back together. Once the DNA is securely split RNA Primase comes in and synthesizes (in the 5->3 direction) an RNA primer only a few nucleotides long. This makes it possible for DNA Polymerase III to come in and start making DNA, DNA Polymerase III needs something to build on, it can not just start on its own so it needs to be primed (hence the name RNA primase). Once the DNA Polymerase III has attached and started making DNA in the 5->3 direction we need to get rid of the RNA, so DNA Polymerase I comes in and removes the primer and replaces it with DNA. Once DNA Polymerase I is complete we still have these little breaks in the backbone that need to be fused together and that is exactly what DNA Ligase does. It rides along the newly formed DNA stand and fuses any breaks in the backbone that way we have a solid strand of DNA!
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