1. Structure of DNA

2. What is DNA? Deoxyribo- Nucleic Acid Stores hereditary information
It’s stored in the nucleus
A segment of DNA is called a gene
DNA controls all of the activities of the cell
Every cell contains a complete copy of DNA
Prokaryotic cells-DNA is in the cytoplasm
Eukaryotic cells-DNA is contained In nucleus

3. DNA is Made of Nucleotides
DNA is a string of nucleotides.
What is a nucleotide?
a sugar, a phosphate,
and a nitrogenous
base
’s leading scientists thought DNA just a bunch of simple nucleotides

4. 4 different nitrogen bases= 4 different nucleotides
Purines Pyrimidines
Adenine
Thymine
Cytosine
Guanine A T G C
2 rings of carbon ring of carbon

5. 4 Bases Always Pair the Same Way
Base Pairing Rules:
Adenine-Thymine
Guanine-Cytosine

6. Anti-Parallel Strands
Strands run in opposite directions.

7. The Double Helix Model
DNA resembles a twisted “ladder” or “double helix”
“Rails” or sides are made up of a sugar-phosphate backbone
“Rungs” or steps are made up of nitrogenous bases
Rungs
or Steps
Rails or
Sides
Rails
or Sides

8. Nucleotide: one sugar, one phosphate, one nitrogen base.
REVIEW:
Nucleotide: one sugar, one phosphate, one nitrogen base.
4 Bases:
Adenine
Guanine
Cytosine
Thymine
Base Pairing Rules:
Adenine = Thymine
Guanine = Cytosine
Nucleotide Bases 3’ 5’
sugar &
phosphate
backbone 3’ 5’
Go back to first slide and review
Anti-Parallel Strands