1. Unit 4 Notes: DNA Structure

2. (1) What is DNA? DNA = DeoxyriboNucleic Acid
Stores genetic instructions for producing proteins.
Stored in the Nucleus of Eukaryotes.

4. (2) Overall DNA Structure
Double stranded
Helix
Outside / Backbones Made Of:
Alternating Phosphates and Sugars
Inside / Steps Made of:
Nitrogenous Bases

6. (Yes You Need To Draw This…)

7. (3) DNA Nucleotide A nucleotide is the monomer for DNA. Structure:
Phosphate
Deoxyribose Sugar
Nitrogenous Base
Looks Like:

8. (4) Nitrogenous Bases
The sequence of these bases ARE your genetic code/instructions.
4 Types of Bases:
A = Adenine
T = Thymine
G = Guanine
C = Cytosine
A’s and T’s bond together.
G’s and C’s bond together.

9. GUANINE
ADENINE
CYTOSINE
THYMINE

11. (5) Chargaff’s Rule (%A + %T) + (%G + %C) = 100%
Chargaff discovered how the bases pair together in DNA.
He found that:
% of A bases = % of T bases
% of G bases = % of C bases
We can use Chargaff’s Rule to find exact concentrations of bases:
(%A + %T) (%G + %C) = 100%

12. …And that if we take %A + %T + %G + %C it equals 100%!
Do you see how all of the %’s of A and T are about equal?
Do you see how all of the %’s of G and C are about equal?
…And that if we take %A + %T + %G + %C it equals 100%!

13. (6) Chargaff’s Rule Example:
Within the DNA of yeast cells, it is found that 16% of the bases are Adenine…
What % are Thymine?
What % are Guanine or Cytosine?

14. (7) Anti-Parallel Strands:
Anti-Parallel refers to the two strands in DNA being positioned in opposite directions.
The strands are upside down mirror images of one another!