1. 12 – 1 DNA

2. Gene – is a portion of DNA that codes for a specific Trait
DNA – Genetic material of living organisms and is located in the chromosomes of each cell.
Gene – is a portion of DNA that codes for a specific Trait
A. DNA is made of two chains of repeating subunits called nucleotides -
B. Each nucleotide consists of three parts:
1. Deoxyribose: a 5-carbon sugar molecule
2. A phosphate group: made of P surrounded by oxygen
3. Nitrogenous base: basic molecule that contains nitrogen

4. 2. Four nitrogenous bases A. Purines (2 carbon rings)
1. Adenine = A
2. Guanine = G
B. Pyrimadines (1 carbon ring)
1.Cytosine = C
2. Thymine = T

6. 3. The Double Helix
A. Made of two nucleotide chains that wrap around each other to form a spiral staircase.
B. Backbone - Alternating sugar and phosphate groups.
C. Rungs - Hydrogen bonds hold opposing bases to each other, perpendicular to backbone.

7. A. Base-pairing rules: B. One purine bonds with one pyrimadine
4. Complementary Base Pairing
A. Base-pairing rules:
1.Cytosine always bonds with guanine
a.3 hydrogen bonds
b. C - G
2. Adenine always bonds with thymine
a. 2 hydrogen bonds
b. A - T
B. One purine bonds with
one pyrimadine