DNA Structure DNA Backbone 5 1 4 2

DNA Structure

DNA Backbone 5’ 1’ 4’ 2’ 4’ 1’ 3’ 2’

DNA Backbone Describe the chemical structure of the DNA backbone. What is meant by 5’ to 3’? Antiparallel.

Nitrogenous Bases

Complementary Base Pairing Chargaff’s Rule ? Base pair diameter is 2 nm.

Overall DNA Structure Right handed helix 0. 34 nm between adjacent base pairs One turn of the helix is 10 base pairs (3. 4 nm)

Genetic Mechanisms

Genetic Mechanisms Replication Transcription Translation

DNA Replication pp 282 - 290 Practice Questions pg 290, #3, 7, 8, 10

DNA Replication

Replication Theories

1958 – Meselson & Stahl Grew E. coli in 15 N media Start the experiment with DNA that only contained 15 N atoms.

Replication Theories Only one DNA is labeled 15 N-labeled DNA One strand of both DNAs labeled Both strands of both DNAs labeled

Meselson & Stahl Experiment Conclusion What was the conclusion of their experiment? .

Replication in Organisms

Replication Three main steps to replication: 1. 2. 3.

1. Replication Initiation Origins of replication (ori)

1. Replication Initiation DNA helicase – single-stranded binding proteins (SSBPs) – Know the opposite concepts of Denaturing Reannealing DNA Replication Animation

Helicase Animation DNA Helicase Activity

1. Replication Initiation replication fork –

1. Replication Initiation DNA gyrase –

1. Replication Initiation replication bubble –