+January 7, 2015

Objectives:To understand how DNA was

discoveredTo be able to model the structure of

DNA

Journal:

Do you think that people have always known that DNA carries our genes? How do you think it may have been discovered?

*** Hand in Race for DNA Structure Worksheet

+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

+Experiments that Determined DNA was the Genetic Material in Cells

Griffith’s Discovery of TransformationDiscovered that genetic material could be

transferred between cells

Hershey-Chase ExperimentDetermined that DNA is the hereditary

material instead of proteins

Rosalind Franklin and Maurice WilkinsTook pictures of DNA using x-ray

diffraction

+Experiments that Determined the Structure of DNA

ChargaffDetermined amount of A = T,

C=G

James Watson and Francis CrickBuilt model of DNACredited 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.

Nucleotide Structure – basic building block of DNA

SugarPhosphate GroupNitrogen Base

SugarN. Base

P

Building blocks of DNA

+

1. Adenine

2. Guanine

4. Cytosine

3. Thyamine

Four Different Nitrogen Bases

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’

Sides of the staircase = sugar & phosphates

Steps of the staircase = nitrogen bases.

Spiral Staircase Structure

Base Pairing Rule:

A – T held together by two hydrogen bonds

C – G held together by three hydrogen bonds

Purines vs. Pyrimidines

Purines Structure has two rings Adenine and Guanine

Pyrimindines Structure has one ring Cytosine and Thymine

+The Race for DNA Structure Video

https://www.youtube.com/watch?v=d7ET4bbkTm0