DNA Replication Replication Facts DNA has to be
DNA Replication
Replication Facts DNA has to be copied before a cell divides DNA is copied during mitosis and meiosis (cell division) New cells will need identical DNA strands
DNA Replication Two strands of the DNA molecule open forming replication forks New strands grow at the forks 5’ 3’ 3’ Parental DNA Molecule Replication Fork 5’
DNA Replication As the 2 DNA strands open at the origin, replication bubbles form Prokaryotes (bacteria) have a single bubble Eukaryotic chromosomes have MANY bubbles Bubbles
DNA Replication Helicase “unzips” and separates the 2 DNA strands by breaking the weak hydrogen bonds Binding enzymes attach and keep the 2 DNA strands separated.
DNA Replication Before new DNA strands can form, the enzyme primase prepares for the addition of new nucleotides DNA polymerase can then add the new nucleotides
Remember!! The Strands are Antiparallel 5 O 3 3 P 5 O O C G 1 P 5 3 2 4 4 P 5 P 2 3 1 O T A 3 O 3 5 O 5 P P
Synthesis of the New DNA Strands The leading strand is synthesized as a single strand from the point of origin toward the opening replication fork 5’ 3’ Nucleotides DNA Polymerase Primase 5’
Proofreading New DNA polymerase initially makes about 1 in 10, 000 errors Other enzymes proofread and correct these mistakes The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors
The Semiconservative Nature of Replication The two strands of the parental molecule separate, and each acts as a template for a new strand New DNA has 1 ORIGINAL and 1 NEW strand of DNA Template Parental DNA New DNA
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