DNA replication and transcription
- Created by: Alice Fisher
- Created on: 05-05-15 13:39
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- DNA replication and transcription
- DNA replication
- Semi-conservative;each new stand has one from parental helix
- Synthesis initiated by creating a replication fork where DNA strands are separated. New strands have an antiparallel orientation.
- Leading strand and lagging strand
- Lagging strand requires a discontinuous backstitchingso that only 5' to 3' DNA polymerase needed
- Requires an RNA primer sequence which is then extended by DNA polymerase and then removed by RibonucleaseH (leading)
- For lagging, every time DNA polymerase completes a fragment, it must start synthesising a new one further along
- Involves DNA primase synthesising short RNA primers
- DNA ligase covalently links the Okazaki fragments
- DNA helicase continuously unwinds the strands. Single stranded binding proteins (SSB's) maintain the single strands
- Leading strand and lagging strand
- DNA transcription
- Initiation occurs by binding of RNA polymerase to the promoter defining starting position
- One RNA copy produced for each reading and end dictated by specific terminator signals
- Eucaryotes has 3 phases; Initiation, elongation and termination
- Exons present in mRNA while introns spliced out by spliceosomes
- RNA processing (splicing, capping and polyadenylation) all occur in cell nucleus
- Initiation occurs by binding of RNA polymerase to the promoter defining starting position
- DNA replication
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