DDeoxyriboeoxyribonnucleic ucleic AAcidcid

DNADNA

Organism

Cell

Chromosome Gene

DNA

Nucleotide

I. The Structure of DNAA. DNA Structure1. Winding Staircase

a. DNA is made of chains of nucleotidesb. The strands are twisted into the form of a double helix.

2. Nucelotidesa. Each Nucleotide in DNA is made up of the sugar deoxyribose, a phosphate group and one of four nitrogenous bases.b. The four nitrogenous bases found in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T)

3. Pairing Between Basesa. The two strands of DNA are complimentaryb. Each A on one strand pairs with a T on the opposite strand.

c. Each C on one strand pairs with a G on the opposite strand.

B. Discovering DNA’s Structure1. Erwin Chargoff’s Observations

a. Chargoff’s data showed that for each organisms the amount of Adenine equaled the amount of Thymine.b. Likewise the amount of Cytosine equaled the amount of Guanine.

2. Wilkins’ and Franklin’s Photographs – Wilkins’ and Franklin’s X-ray diffraction photographs supported that DNA is a tightly coiled double-helix.

3. Watson and Crick’s DNA Modela. Watson & Crick determined the structure of DNA in 1953 with the help of data gathered by Wilkins,Franklin and Chargoff.b. Watson, Crick and Wilkines won the Nobel Prize in 1962

Erwin Chargoff Rosalind Franklin Maurice Wilkins

X-ray diffraction image of DNA

James Watson & Francis Crick

II. The Replication of DNAA. DNA Replication1. Before a cell divides, it copies its DNA by a process called

replication.2. The results of DNA replication is duplication of the cell’s

original DNA.3. Each new double helix is composed of one original and one

new DNA strand.B. DNA Replication Enzymes 1. In DNA replication, enzymes work to uncoil the DNA strands2. Unzip the two strands3. Add complimentary nucleotides to the exposed strands.C. Checking for Errors 1. DNA polymerase proof-reads DNA during its replication 2. Because of this, very few errors occur.

The End