DNA
"The Blueprint of Life"
Rosalind Franklin
•
1952, Rosalind Franklin used x-ray crystallography to take
a picture of DNA
X-Ray cyrstallography
A little history lesson….
• 1953: James Watson
(twenty-five years old at the
time) and Francis Crick
(right) established that the
structure of a DNA was a
double helix.
• In 1962, Watson, Crick and
Maurice Wilkins shared the
Nobel Prize
• Rosalind Franklin, who had
died very young in 1958,
was not included in the Prize
despite her work being
crucial to Watson and Crick.
DNA stands for...
DeoxyriboNucleic Acid
●Codes for your genes (traits)
●Made of repeating subunits called
nucleotides
What is a nucleotide?
Has three parts:
1. PHOSPHATE
2. DEOXYRIBOSE (sugar)
3. BASE (A,T,G,C)
Phosphate
Base
Sugar
Base-Pair Rule
Adenine <==> Thymine
Guanine <==> Cytosine
• The sides of the DNA
ladder are phosphate &
sugar
• The steps of the ladder
are made of nitrogen
bases that are held
together by hydrogen
bonds
Base Pair Rule
One side:
Other side:
A T A
T C A
T G C
G G G
T A T
A G T
A C G
C C C
Nitrogen Bases
Phosphate and
Sugar
Two strands form the DOUBLE HELIX
What is the relationship between GENES and DNA?
How the Code Works
The combination of A,T,G,C determines what
traits you might have.....
C A T C A T = purple hair
T A C T A C = yellow hair
Think of the bases of DNA like letters.
Letters form words....
Words form sentences....
*endless
combinations
Genetic Code
• “Words” and “Sentences” are
called genes.
• Humans have 20,000 – 25,000
genes that code for traits.
• These genes tell a cell what
proteins to make.
• It is the proteins that give you
your traits. For example,
brown hair, blue eyes, etc.
Let's Review What We Know About DNA
1. DNA stands for: De _____ ribo ______ acid
2. What is the shape of DNA? ______________
3. Who established the structure of
DNA? ____________ and ______________
4. Adenine always pairs with _______________
5. The sides of the DNA ladder are deoxyribose
and _______________
6. Guanine always pairs with _____________
7. What is the complementary sequence:
C
A
T
T A G
8. The two sides of DNA are held together by
_______ bonds.
9. DNA is composed of repeating subunits called
______________________
10. What are the 4 bases that make up the rungs
of the DNA ladder? ____________________
Let's Review What We Know About DNA
1. DNA stands for: De _____ ribo ______ acid
2. What is the shape of DNA? ______________
3. Who established the structure of
DNA? ____________ and ______________
4. Adenine always pairs with _______________
5. The sides of the DNA ladder are deoxyribose
and _______________
6. Guanine always pairs with _____________
7. What is the complementary sequence:
C
A
T
T A G
8. The two sides of DNA are held together by
_______ bonds.
9. DNA is composed of repeating subunits called
______________________
10. What are the 4 bases that make up the rungs
of the DNA ladder? ____________________