Download - DNA Replication How to copy a genome
DNA Replication
How to copy a genome
DNA Replication
When: During S-phase of interphase
Where: Prokaryotes – in nucleoid region Eukaryotes – in the nucleus
How: Starts at origin of replication Uses a variety of proteins
Result: Two identical DNA molecules
Origin of Replication
Where replication begins
Prokaryotes1 origin
Eukaryotesmultiple origins
for each chromosomes
Terminology
Replication Bubbleseparated double helix
Replication Forkone at each end of bubble, where helix is
actively unzippedSemi-conservative
each new helix contains half of the parent strand
Replication Overview
Enzymes involved in Replication
DNA Polymerase I replaces RNA
primer with DNA DNA Polymerase III
adds DNA nucleotides to elongating strand
DNA Ligase connects DNA
backbones
RNA Primase adds RNA primer
Helicase unzips double helix
Single-Strand Binding Proteins keeps helix
separated
Steps in DNA replication
Step 1: Unwinding DNA Step 2: Addition of RNA primerStep 3: ElongationStep 4: Primer removal and Ligation
Step 1: Unwinding DNA
Helicase attaches to double helix, unwinds DNA, and separates complimentary base pairs
Single-strand binding proteins attach to DNA to prevent helix reforming
Step 1: Unwinding Double Helix
SS binding proteins
Step 2: Addition of RNA primer
RNA primase adds RNA primer to lagging strand
RNA primer: short RNA nucleotide molecule complimentary to template strand
Template (parent) strand: pre-existing DNA stand
Step 2: Addition of RNA primer
RNA Primase
Leading Strand
Lagging Strand
Step 3: Elongation
DNA polymerase III adds DNA nucleoside triphosphates complimentary to templates strand
Lagging strand – DNA polymerase III starts elongation at RNA primer
Polymerase works only in the 5’ 3’ direction
Step 3: Elongation
Nucleoside Tri-phosphates
Nucleoside Tri-phosphate
Step 4: Primer removal and Ligation
DNA polymerase I removes RNA primer and replaces RNA nucleotides with DNA nucleotides
DNA backbone between fragments are joined (ligated) by DNA ligase
Step 4: Primer removal and Ligation
Enzyme Overview
Replication Overview
Animation
DNA Replication 1DNA Replication 2DNA Replication 3 – cool sounds