Unit V: Molecular Genetics

Part III: DNA REPLICATION

Quick Review•A pairs with T•C pairs with G•Hydrogen bonds hold the bases together•One DNA molecule = two strands•Antiparallel (opposite)

Key Factors•Replication Forks: sites where separation & replication of DNA occur•DNA Polymerase:

1. Joins nucleotides to produce new DNA molecule2. “Proofreads” each new strand to make sure that each new strand of DNA

is identical to the original

What is DNA Replication?•A process where DNA is copied •In what phase of Interphase is DNA replicated?

When?•DNA replication occurs during the S phase in Interphase

•Is interphase apart of mitosis?

Where?•In eukaryotes, DNA replication occurs in the NUCLEUS

•In prokaryotes, DNA replication occurs in the CYTOPLASM

Steps of DNA Replication

Step 11. DNA helicase “unzips” the DNA

molecule into two strands•Breaks the Hydrogen bonds between the nitrogenous bases•Forms replication fork

Step 22. Each separated strand now

serves as a template to produce new strands!•Primase = enzyme that acts as

the “green light” for replication to start

Step 33. DNA Polymerase attaches

to the single strands•Help make two new DNA strands

by base pairing• A-T, G-C

•New double strands of DNA are IDENTICAL

Step 44. DNA Ligase ”glues” the

new DNA molecules together•Forms Hydrogen bonds

between the nitrogenous bases

Results In…•2 IDENTICAL DNA molecules•Each molecule is made up of one old strand and one new strand

• https://www.youtube.com/watch?v=5qSrmeiWsuc