1. DNA DeoxyriboNucleic Acid

2. What can DNA do? Carries information from one generation to the next
Determines the heritable characteristics of organisms
Genes must be easily copied

3. DNA Structure DNA is a long molecule made up of units called
Nucleotides
3 basic components
5-carbon sugar
(deoxyribose)
Phosphate group
Nitrogenous base

4. Nitrogenous Bases There are four Nitrogenous Bases
Purines: Two rings in their structures
Adenine
Guanine
Pyrimidines: One ring in their structure
Cytosine
Thymine
Have a “Y”

5. Backbone of DNA Twisted Ladder: Double Helix
Sides: Formed by sugar and phosphate groups of each nucleotide
-Held together by weak hydrogen bonds
Steps:The nitrogenous bases stick out sideways from the chain

6. Chargaff’s Rules Base pair rules Adenine always pairs with Thymine
Cytosine always
pairs with Guanine

7. Nitrogen Base Pairs…..
If 28% of the bases of a certain segment of DNA are guanine, then what is the percent of the bases are cytosine?
If 30% of the bases of a certain segment of DNA are thymine, then what is the percent of the bases are adenine?

8. Double Helix Rosalind Franklin Watson and Crick
Used X-ray diffraction to show helical DNA
Had the evidence that the double helix existed but didn’t put it all together
Watson and Crick
Tried to put together a model of DNA
Wasn’t until they saw Franklin’s X-rays that they discovered the double helix pattern

9. We are all nearly the same?
ALL organisms have the same DNA structure and nitrogen bases
Only the amount and sequence of ATGC differentiates the species
Ex: The person sitting next to you is only .01% different in their DNA