Replication of DNA Flashcards
What is DNA replication ?
The production of two new DNA double-helix molecules each consisting of one parental strand and one daughter strand
What is DNA replication also known as?
SEMI-CONSERVATIVE REPLICATION OF DNA
What are the 4 conditions for DNA replication?
- A pool of the four types of nucleotides must be present.
- Both strands of the DNA being copied, act as a template.
- The enzyme, DNA Polymerase must be present.
- A source of energy (ATP) is required to drive the process.
What is the first step of DNA replication?
- base pairing allows each strand to serve as a template for a new strand
- new strand is 1/2 parent template & 1/2 new DNA
What is step 1 of DNA replication?
The enzyme DNA helicase breaks the hydrogen bonds holding the base pairs together (‘unzips’ the DNA).
What is step 2 of DNA replication ?
- DNA helicase completes the splitting of the strand.
- Meanwhile, free nucleotides that have been activated are attracted to their complementary bases.
- Each chain acts as a template.
What is step 3 of DNA replication ?
- Once in place the activated nucleotides are joined together by DNA polymerase.
- DNA polymerase joins the new nucleotides to each other by strong covalent bonds (phosphodiester bonds), forming the phosphate-sugar backbone.
What is the final step of DNA replication ?
The result is that there are two DNA molecules, each with one new synthesised strand of DNA and one strand from the original.
What is the leading strand ?
As the DNA is unzipped the enzyme DNA polymerase adds new nucleotides (A bonds with T and C bonds with G) to the 3’ end (in a 5’ direction) of the original strand producing a continuous strand.
What is the lagging strand?
DNA polymerase can only add nucleotides to the 3’ end of the original strand therefore DNA polymerase must work from the replication fork down the strand producing small fragments – Okazaki fragments – that are later joined together by DNA ligase.
