Download The Structure of DNA

The Structure of DNA
The Double Helix
DNA = Deoxyribonucleic acid
• DNA is made up of small sub units
called Nucleotides
• A Nucleotide Has 3 major parts
-Sugar (Deoxyribose)
-Phosphate Group
-Nitrogen Base
Phosphate
Sugar = Deoxyribose
Nitrogen Base
•
•
•
•
Adenine
Guanine
Thymine
Cytosine
• Uracil is used
only in RNA
A single strand of DNA looks a little
like this:
Two Strands of DNA are held
together by hydrogen bonds
The double helix:
• refers to two
stands of DNA
held together
by hydrogen
bonds between
complementary
Nitrogen
bases.
Nitrogen bases fit together like
puzzle pieces
•
•
•
•
Cytosine bonds to Guanine
Adenine bonds to Thymine
These “bases” make the steps on a ladder
The Phosphate and sugar
Makes the “Backbone”
A closer look at a bacteria Chromosome
When DNA is not being used it is
tightly coiled around proteins called
“Histones” to form a Chromosome
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
How did they discover the
structure?
• Rosalind Franklind took
this X-ray Diffraction Picture
• James Watson and
Francis Crick used the photo as
they were developing their model… They
never gave her credit for her work and she
died of ovarian cancer likely due to
exposure to the X-rays of her work
Images From
• Prentice Hall Presentation Pro CH 12
• http://en.wikipedia.org/wiki/Photo_51
• http://en.wikipedia.org/wiki/Rosalind_Frank
lin
• http://en.wikipedia.org/wiki/DNA