Prokaryote Dna Synthesis Lab Report

Prokaryote DNA replication is a semi conservative, bidirectional, template driven process. The phrase ‘semi-conservative’ refers to the fact that the newly synthesised double stranded DNA is made up of one parental (existing) strand, and one newly synthesised strand. The parental duplex is not ‘conserved’ as an entity. This was proved by the Meselson-Stahl experiment by replicating E.Coli in different mediums of of different Nitrogen isotopes. The results consisted of half of normal weight and half with intermediate weight, proving an immortal strand serving as an unchanging template. It’s bidirectional nature stems from the presence of a replication fork and bubble at the initiation and throughout replication. Replication begins at one consensus sequence (single nucleotide) consisting mostly of repeating AT base pairs. As the processes proceeds both directions (toward and away from) the V-shaped replication …show more content…
A group of three proteins known as the ‘prepriming complex’ are responsible for unwinding the double helix and keeping it separated. The first step is carried out by the DnaA protein. It binds to the origin nucleotides resulting in an AT rich region. The AT rich region sparks the separation of the double strand into single strands of DNA, the ATP dependent process of melting. DNA helicases are responsible for unwinding the helical structure of DNA. They bind to the single stranded DNA created by DnaA protein and move toward the double stranded DNA, turning it into single strand by forcing the strands apart. DnaB helicase is the primary helicase in action in E.Coli. The last part of the prepriming complex is single stranded DNA-binding proteins (SSB). Their job is to create the single stranded template required for the actions of polymerases and to protect the DNA from degradation by nucleases. SSB proteins bind to the single stranded DNA made by the helicases and keep them