Unit 4 Notes: DNA Structure

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

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

(Yes You Need To Draw This…)

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

(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.

GUANINE ADENINE CYTOSINE THYMINE

(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%

…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%!

(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?

(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!