How does DNA copy itself? DNA Replication

 The “parent” strands act as templates for replication  Each receives a new, complementary strand

Produces?  2 new strands of DNA  Each has 1 original parent strand & 1 new complimentary strand  “Semiconservative”

How does Replication happen?  DNA unwinds –Hydrogen Bonds are broken –Done by the enzyme helicase –Strands are held apart by a protein

How does Replication happen?  Replication bubbles are produced –There are many of them along the strand to speed up replication  Half of the bubble is called a Replication Fork

 New strand begins to build –Done by DNA polymerase (enzyme)  Cannot build it from scratch –Builds on pre-existing strand (parent strand) Building of New Strands

How does it do this without Energy?  IT DOESN’T!!!  There must be energy! –When a nucleotide joins the strand, phosphate groups are broken off  This releases Energy!

Are the strands formed at the same time and in the same way?  No!  One strand is the Leading Strand –built in the same direction that the helix unwound

Lagging strand  The other strand is the Lagging Strand –Built in the opposite direction that the helix unwound  Built in sections

How do we get two strands?  The replication bubbles replicate until they grow together

Two Identical Strands  When the replication bubbles have grown together you are left w/2, strands of DNA!

What if there are errors?  DNA polymerase can “proofread” and fix mistakes

What if it misses the mistake?  The change in nucleotide sequence (error) is a mutation  Only 1 error per 1 billion nucleotides

DNA Replication  Watch! Watch!