DNA: The Genetic Material

The Structure of DNA The Replication of DNA

The Structure of DNA

A winding staircase Discovering DNA’s structure – Chargaff’s observations – Wilkins and Franklin’s Photographs – Watson and Crick’s DNA model.

The Structure of DNA DNA- Deoxyribonucleic Acid Structure founded by James Watson, Francis Crick, and Rosalind Franklin (the woman who never receives credit) Double Helix structure: Two strands twisted around each other.

The Structure of DNA Double helix with each strand linked together with nucleotides. Nucleotides: Subunits that make up DNA. – Phosphate Group – Five-carbon sugar molecule – Nitrogen-containing base.

The Structure of DNA Nucleotide

The Structure of DNA

4 different types of nitrogenous bases.

The Structure of DNA

Discovering DNA’s Structure Chargaff’s observations Wiklin’s and Franklin’s Photos Watson and Crick’s DNA model Pairing Between Bases

Discovering DNA’s Structure Erwin Chargaff The amount of adenine = the amount of thymine. The amount of guanine equaled the amount of cytosine. – What could this tell you about the structure of DNA?

Discovering DNA’s Structure Wilkin’s and Franklin’s Photographs X-ray diffraction Shoot rays at a molecule and observe its structure.

Discovering DNA’s Structure Watson an Crick used Franklins data, initially without her knowledge. Created a tin-wire model of the double helix. These gentlemen were well known, rich, white men and is why they were able to suppress a woman’s findings.

Discovering DNA’s Structure

Base-pairing rules were aided in creation by Chargaff’s rules. Adenine pairs with thymine. Guanine pairs with cytosine. Pyrimidine is always paired with a purine.

Discovering DNA’s Structure The sequence of bases on one end, determines the sequence of bases on the other. The bases are represented by their first letter below: 1 strand of DNA= TCGAACT What would the complimentary strand’s base pairs be?

Discovering DNA’s Structure

The Replication of DNA Roles of enzymes in DNA replication – Checking for errors – Rate of replication Why would DNA need to replicate??

The Replication of DNA DNA Replication: The process of making a copy of DNA. When does DNA replication occur?

The Replication of DNA

DNA Helicase unzips the genes. This breaks the hydrogen bonds between base pairs and unwinds the double helix. DNA Polymerase adds nucleotides to the templates strands according to base pair rules. The nucleotide sequence in both of the new strands is the same as the original.

The Replication of DNA Should there be an enzyme to check DNA replication? To make sure there are no errors?

The Replication of DNA DNA polymerase acts as a “proofreader” for DNA replication.

The Replication of DNA