DNA Replication Flashcards
Why is the process of DNA replication described as semi-conservative
Considered semi-conservative as the double-stranded molecule will divide into two parent strands. One of the strands is retained from one generation while the other is new.
what are three enzymes involved in the DNA replication process?
- helicase
- DNA polymerase
- DNA ligase
what is the function of DNA ligase?
DNA ligase is an enzyme used to catalyse the formation of a bond between two pieces of DNA
what is DNA polymerase
Is an enzyme responsible for collecting nucleotides floating in the nucleus and matching them with the complimentary pairs on the parent strand.
what is the function of helicase
DNA helicase unzips the DNA molecule by breaking the hydrogen bonds between the nucleotides and exposing the nucleotide bases.
what enzyme starts the unwinding process
DNA helicase
describe the unwinding process
DNA helicase unzips the DNA molecule by breaking the hydrogen bonds between the nucleotides.
what is the replication fork
The junction between the unwound single strand of DNA and the intact double helix.
what is DNA polymerase’s unique feature
It can only synthesise in a 5’ to 3’ direction. As DNA is an antiparallel molecule, one strand synthesises in the direction of unwinding and the other in the opposite direction.
what is the leading strand
The leading strand is the DNA strand that is synthesised continuously in a 5’ to 3’ direction. DNA polymerase is moving towards the replication fork.
what is the lagging strand?
The lagging strand is the DNA strand that is synthesised discontinuously in Okazaki fragments in a 5’ to 3’ direction. DNA polymerase is moving away from the replication fork.
describe the synthesis process of the lagging strand
- The lagging strand is replicated in small sections, with the polymerase enzyme constantly detaching and reattaching.
- The strand must have a starting point to attach to.
- The enzyme primase creates short segments known as primers which bind to the lagging strand.
- Polymerase enzyme and this primer make up sections of DNA called Okazaki fragments
describe the process of DNA replication
- helicase unwinds and unzips the DNA molecule
- DNA polymerase adds nucleotides to the present strand reading in a 3’ to 5; direction.
- Leading strand continues
- lagging strand discontinues
- Okazaki fragments form
- DNA polymerase detaches and reattaches
- Primase creates primers for the polymerase to bind to at the start of each Okazaki fragment. - Okazaki fragments are joined by DNA ligase
- DNA strands then recoil around histones
