1. Deoxyribonucleic Acid
DNA
Deoxyribonucleic Acid

2. DNA belongs to the class of organic molecules known as Nucleic Acids
Made up of monomers called nucleotides.
Remember the other organic molecules we studied:
Carbohydrates
Lipids
Proteins

3. Where is it found in the cell?
DNA condenses to form chromosomes
Remember chromosomes are in the nucleus of a cell
There is also a little bit of DNA found in the mitochondria

4. What does it look like? A twisted ladder, known as a double helix.
There are two strands of DNA that make up the double helix

5. A Closer Look at a Nucleotide
Ribose + Phosphate + Nitrogenous Base

6. 4 Different Nitrogenous Bases
Adenine
Guanine
Thyamine
Cytosine

7. Bases are Grouped by Structure
Purines- 2 rings
Adenine
Guanine
Pyrimadines- 1
Cytosine
Thyamine

8. Purines Always Pair to Pyrimidines
Adenine to Thyamine
Guanine to Cytosine
This keeps the lengths of the “rungs” the same length.
Hydrogen bonds form between the purines and pyrimidines

9. What does the ladder look like?
The “rungs” of the ladder are made up of bases.
The sides of the ladder are made up of the deoxyribose and phosphate part of the nucleotide
Notice the deoxyribose and phosphate alternate

11. Rosalind Franklin
Was the first to photograph DNA
But she is rarely given much credit!

12. Q: Who gets the credit? A: Watson and Crick
In 1953, they used Franklin’s photograph and other experimental evidence to come up with the idea that DNA is in the shape of a double helix.

13. We now have lots of evidence to show that Watson, Crick and Franklin were correct about DNA!
Watson and Crick won the Nobel Peace Prize in 1962 for their discovery of the structure of DNA