DNA replication is a semi conservative replication technique

DNA Replication

Complementary base pairings is the key to DNA’s ability to replicate

If they pair together, then you can always figure out the other strand’s nucleotides if you have one strands nucleotides, right?

DNA is unzipped and hydrogen bonds are broken by DNA helicase The 2 strands open at a fork (looks like a Y shape) and the new stransd are made at the fork. The original strand is called the ‘parent DNA’

Enzymes and Process

1. Helicase unwinds and separates the 2 DNA strands (double helix structure) by breaking up the bond
2. Single stranded binding proteins attach and keep the DNA strands separated and stop them from reforming
3. Before they can start copying, RNA primers start the addition of new nucleotides (create a chemical reaction that tells the RNA polymerase to start adding nucleotides)

   Primase is the enzyme that synthesises the RNA primer, which gives a starting point

4. DNA polymerase the adds new nucleotides by finding the corresponding nucleotide (that are free-floating in the cytoplasm) and sticks it in

   DNA can only be synthesised in the 5’ to 3’ direction, so when copying the 3’ to 5’ strand, RNA primers have to go and start the reaction, with RNA polymerase only being able to do 3-4 nucleotide chunks at a time. It has to backtrack, and these chunks are called Okazaki fragments.

   The 5’ to 3’ strand is called the leading strand, the 3’ to 5’ strand is called the lagging strand

5. DNA ligase makes sure all nucleotides have been bonded together and joins the fragments toether

Error Checking

1 in 10000 nucleotides have an error; enyzmes proofread and correct these errors If an enzyme spots the error, this particular error’s chance of occuring is reduced to around 1 to 1 billion.