+IBDP Biology post, we will see how the DNA replicated, and what enzymes are involved with DNA replication.
DNA Replication
DNA is kept in a double helix by:
- phospo-diester bonds of the sugar-phosphate backbone
- hydrogen bonds between the complementary bases
DNA Replication in Prokaryotes can only be initiated at one point
DNA Replication in Eukaryotes can be initiated at many points
Standard Level
1. DNA Helicase unwinds the and unzips DNA
The two strands are seperated by breaking Hydrogen bonds between complementary base pairs. The two separated strands become Template strands
2. DNA Polymerase creates complementary strands
DNA Polymerase always moves in a 5' to 3' direction. It catalyses the phopodisester bonds between sugar and phosphate molecules.
HIGHER LEVEL
RNA Primers provide an attachment and initiation point for DNA Polymerase iii
RNA Primers: Short sequence of RNA nucleotides
DNA Replication moves in a 5' to 3' direction. The 5' is the end to which a new nucleotide attaches
Leading Strand: DNA is being replicated continously in a 5' to 3' direction
Lagging Strand: DNA is being replicated discontinously in small fragments in the 5' to 3' direction away from the replication fork
DNA Polymerase iii adds free nucleotides to C3. The strand grows from the 3' end
New strand: 5' to 3' direction
Template strand 3' to 5' direction
Two new strands which are identical to the Template strand
Semi-Conservative: New strand contains one new and one template strand
Enzymes involved in DNA Replication
1. DNA Gyrase: Relieves strain and prevents supercoiling of DNA double helix
2. DNA Helicase: Unwinds and seperates double stranded DNA by breaking Hydrogen bonds between Complementary bases
3. RNA Primase: Synthesizes a short RNA Primer on each template strand to provide an attachment and initiation point for DNA Polymerase iii
4. DNA Polymerase iii: Adds nucleotides to the 3' end of the polynucleotide chain, synthesizing in a 5' to 3' direction
5. DNA Polymerase i: Removes the RNA Primers and replaces them with DNA
6. DNA Ligase: Joins the Okazaki fragments together to create a continuous strand
That's the end ! Well done!
References:
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fbyjus.com%2Fbiology%2Fdna-replication-machinery-enzymes%2F&psig=AOvVaw2FeASQjuDWAJbjXXCkAcCg&ust=1626194915570000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCPDBuaX-3fECFQAAAAAdAAAAABAD
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fjackwestin.com%2Fresources%2Fmcat-content%2Fdna-replication%2Fspecific-enzymes-involved-in-replication&psig=AOvVaw2FeASQjuDWAJbjXXCkAcCg&ust=1626194915570000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCPDBuaX-3fECFQAAAAAdAAAAABAJ
Drafted by Venetia (Biology)