1. DNA REVIEW
Objective: To review the structure and function of DNA.

2. Introduction
You are made up of billions of cells and each cell has its own unique set of 46 chromosomes.
A chromosome is just one big long chain of DNA!
DNA (Deoxyribonucleic Acid) contains all the information that determines who you are!

3. DNA DNA is often called the blueprint of life.
DNA contains the instructions for making proteins within the cell.

4. Chromosomes and DNA Our genes are on our chromosomes.
Chromosomes are made up of DNA.

5. The Shape of the Molecule
DNA is a very long polymer. (chain of nucleic acids)
Its basic shape is like a twisted ladder or zipper.
It is called a double helix.

6. The Double Helix Molecule
The DNA double helix has two strands twisted together.

7. One Strand of DNA
phosphate
The backbone of the molecule is alternating phosphates and deoxyribose sugar.
Nitrogenous bases are attached to the backbone.
deoxyribose
nitrogenous bases

8. Four nitrogenous bases
DNA has four different bases:
Cytosine C
Thymine T
Adenine A
Guanine G

9. Thymine and Cytosine are pyrimidines.
Thymine and cytosine each have one ring of carbon and nitrogen atoms. C N O
cytosine C N O
thymine

10. Adenine and Guanine are purines.
Adenine and guanine each have two rings of carbon and nitrogen atoms. C N O
Guanine C N
Adenine

11. Two Stranded DNA
Remember, DNA has two strands that fit together something like a zipper.
The teeth are the nitrogenous bases but why do they stick together?

12. Hydrogen Bonds The bases attract each other because of hydrogen bonds.
Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA.
To the right: Cytosine and Guanine hydrogen bonded

13. Hydrogen Bonds, cont. When making hydrogen bonds:
Cytosine always pairs up with Guanine.
Adenine always pairs up with Thymine.
To the right: Adenine and Thymine hydrogen bonded

14. Important: Adenine and Thymine always join together A T
Cytosine and Guanine always join together
C G

15. BRAINPOP DNA