7. (3) DNA Nucleotide
• A nucleotide is the monomer for DNA.
• Structure:
– Phosphate
– Deoxyribose Sugar
– Nitrogenous Base
• Looks Like:
8. (4) Nitrogenous Bases
• 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.
11. (5) Chargaff’s Rule
• 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. 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.
• One Strand goes 5’ 3’…
and the other starts at 3’ 5’…
• The strands are upside down mirror images
of one another!