Objectives: To understand how DNA was discovered To be able to model the structure of DNA Journal: What is the function of DNA?

The Discovery of DNA Before the 1950s, scientists weren’t sure what genes were made of There was a race between the best scientists in the world to figure it out Through experiments they figured out DNA was the hereditary material

Experiments that Determined the Structure of DNA Rosalind Franklin and Maurice Wilkins Took pictures of DNA using x- ray diffraction Chargaff Determined amount of A = T, C=G James Watson and Francis Crick Built model of DNA Credited with actually discovering DNA structure

Function of DNA Contains the information on how to make proteins. Proteins are the workers to put together and run a cell.

Sugar Phosphate Group Nitrogen Base Building blocks of DNA Nucleotide Structure – basic building block of DNA Sugar Phosphate Group Nitrogen Base P Sugar N. Base

Four Different Nitrogen Bases 1. Adenine 2. Guanine 3. Thymine 4. Cytosine

DNA Structure Double Stranded Helix

Antiparallel Strands DNA strands run antiparallel, opposite of each other One runs from 5’ to 3’ the other runs from 3’ to 5’

Spiral Staircase Structure Sides of the staircase = sugar & phosphates Steps of the staircase = nitrogen bases.

Base Pairing Rule: A – T held together by two hydrogen bonds C – G held together by three hydrogen bonds

Purines vs. Pyrimidines Pyrimindines Structure has one ring Cytosine and Thymine Purines Structure has two rings Adenine and Guanine