1. Chapter 12
DNA and GENES

2. Structure and Function of DNA
Deoxyribonucleic Acid
-- Complex polymer called a nucleic acid
Serves as master copy of information code
Passed with each cell division
Passed from one generation to the next
Composed of repeating nucleotides
Subunit of a nucleic acid

4. Nucleotide Structure Three parts: Simple sugar called deoxyribose
Phosphate group
One of four nitrogen bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

5. Nucleotide Structure A purine joins with a pyrimidine:
Adenine always joins with Thymine
Cytosine always joins with Guanine

6. Nucleotide Chains Nucleotides combine to form a long chain
Two chains joined together at the bases by hydrogen bonds (looks like ladder)
Ladder twists, giving a “double helix” shape

7. Importance of Sequence
ALL DNA has similar structure and function
Four bases offer thousands of possible combinations=
COUNTLESS POSSIBILITIES!!!

8. Replication of DNA DNA must be “copied” every time a cell divides HOW?
Enzymes break down the hydrogen bonds and “unzip” the DNA
Free-floating nucleotides join in to make new pairs
Enzymes reform hydrogen bonds