1. DNA Replication

2. Replication of DNA Replication is the process where DNA makes a copy of itself. Why does DNA need to copy? Simple: Cells divide for an organism to grow or reproduce, every new cell needs a copy of the DNA or instructions to know how to be a cell. DNA replicates right before a cell divides. During replication, the two nucleotide chains separate by unwinding and each strand serves as a template for a new nucleotide chain.

3. DNA replication is semi- conservative DNA replication is semi-conservative. That means that when it makes a copy, one half of the old strand is always kept in the new strand. This helps reduce the number of copy errors.

4. The Players Helicase-enzyme which “unzips” the helix by breaking hydrogen bonds –Begins at origin of replication, creates “Y” replication fork DNA Polymerase-enzyme which builds the new strands of DNA –“reads” base on parent strand, adds complementary base to new strand –Only moves in one direction!!!!-moves 3’(OH) to 5’(P) Leading strand-built continuously, in one piece, toward the replication fork Lagging strand-built in pieces called Okazaki fragments, away from the fork DNA ligase-puts Okazaki fragments together

5. Steps in DNA synthesis…. 1.Helicase unzips helix at origin of rep., forming replication fork 2.DNA polymerase reads bases on leading strand, places complementary nucleotides in place as it moves toward rep. Fork 3.On lagging strand, DNA polymerase builds new strand in Okazaki fragments-DNA ligase joins them together 4.This continues until the ends of the parent strands are reached

6. Origin of replication-where DNA synthesis starts Helicase first binds here

7. Why can’t the lagging strand be built continuously? The replication fork continues to grow and…. DNA polymerase can’t go “backwards”

8. DNA repair DNA polymerase proofreads its work as it goes along & fixes most mistakes!!!!