DNA Replication pp. 200-202

Covalent > Hydrogen What is DNA made of? __________ What type of bond holds a nucleotide together? What type of bond holds the two strands of nucleotides together? Covalent > Hydrogen WHY? MOVIE A

Replication Making copies of DNA Occurs when a cell divides to make new cells The two strands separate and unwind acting as a template to add new nucleotides MOVIE B

First Step DNA is split by an enzyme (helicase), breaking the hydrogen bonds replication fork: point where it separates:

Second Step DNA polymerase adds nucleotides to the open areas ( A-T, G-C) as it unzips Nucleotides attach from surrounding area

Process continues until entire strand is copied Result is two strands of DNA Each strand is 50% new and 50% old DNA (semi-conservative)

Accuracy and Repair Copies must be 100% accurate Mutation= change in nucleotide at one location Enzymes proofread and fix errors