1. Deoxyribonucleic Acid
DNA
Deoxyribonucleic Acid
Watson and Crick

2. How does DNA function?
DNA contains all the genetic information for our cells (and ultimately for our body).
The genes that are made up of DNA tell the
cells which proteins to make.
Those proteins
determine how each
cells functions.
So DNA ultimately
controls all cell
functions.
** Holt Biology Interactive Tutor 6-1

3. What is DNA made from? The monomers of DNA are called nucleotides:
1. nitrogenous base
(adenine, thymine, guanine, cytosine)
2. pentose sugar
(5 carbon sugar called deoxyribose)
3. phosphate group
The nucleotides are assembled (joined) during a dehydration synthesis or condensation reaction.

4. Nucleotide structure:

5. Four Nitrogenous Bases (DNA)
PURINES PYRIMIDINES
A = adenine T = thymine
G = guanine C = cytosine
*Double rings of carbon * Single rings of carbon
and nitrogen. and nitrogen.

6. DNA is shaped like a double helix.
The double helix model indicates that DNA is composed (made) of two nucleotide chains that wrap around each other to form a double spiral...like a spiral staircase or twisted ladder.

7. How do we know about DNA’s shape?
The double helix is the
model proposed by
scientists James Watson
and Francis Crick in 1953.
They received a Nobel Prize
in 1962 for their discovery.
Watson and Crick’s model was supported by evidence from other scientists like Rosalind Franklin and Maurice Wilkins who studied X-ray crystallography (photographs) of DNA.

8. What is the complimentary base pairing rule?
Nucleotides in the chain (backbone) are connected covalent phosphodiester bonds between the phosphate group of one nucleotide and
sugar group of
an adjoining
nucleotide.
This occurs during
a dehydration
synthesis or
condensation
reaction.

9. Complimentary Base Pairing Rule
adenine - thymine (2 hydrogen bonds)
cytosine – guanine (3 hydrogen bonds)
* The sequence in one chain is the exact compliment of the other chain.

10. DNA code: T A C T A G C A A A C T Complimentary sequence would be..?
**Holt Biology Interactive Tutor 6-2
Now you try it...
DNA code: T A C T A G C A A A C T
Complimentary sequence would be..?