Lecture notes
L8 - DNA Replication
- Institution
- Kings College London (KCL)
Lecture by Dr David Chambers
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L8 – DNA ReplicationSlide 3-6 – Overview of Replication
• DNA unwinds
• Daughter strands of DNA produced from parent strand at replication fork
• Semi conservative replication (each new DNA molecule contains one parent and one
daughter strand)
• An identical copy of the DNA parent is synthesised
- Each parent DNA strand is a template for new DNA synthesis
- Parent strand separated (2 daughter strands, white and orange)
- 2 identical copies of daughter cells (one parent strand, one daughter strand)
• New nucleotides are added to the free 3’ OH group of the growing polynucleotide strand
through formation of new phosphodiester bonds by an enzyme (DNA polymerase)
- Daughter cell being synthesised from 5’ to 3’ (left to right), following Watson & Crick
base pairing rules
- Energy required for this process derived from hydrolysis of high energy bonds of
nucleotide triphosphates
, How sugar phosphate backbone is made
- DNA polymerase catalyses esterification reaction between phosphate and sugar
Slide 7-10 – Features of DNA polymerisation
• DNA polymerase requires a single-stranded template
- DNA must be unwound
- Eukaryotic cells: DNA must be removed from histone proteins
• Initiation of replication by proteins interacting with DNA sequences at “origin of
replication”
- Replication origin: first point in the DNA where the hydrogen bonds are made between
nucleotides, where helicase attaches to template strand and starts to unwind the DNA
strands
- Helicase enzyme are able to separate the two strands of DNA
- Initiator proteins: recognise specific DNA sequences within the origin of replication,
allows DNA strands to be pulled apart
- Two “replication forks” are formed
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