DNA DeoxyriboNucleic Acid

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

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

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”

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

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

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?

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

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