DNA

DNA is genetic material
Chromosomes have DNA (4 nucleotides) and proteins (20 AA)
Early hypothesis that genes are made of proteins
Griffith’s experiment
2 strains of bacterium that underwent transformation: rough bacteria picked up smooth strain of DNA and became virulent
Avery, MacLeod, and McCarty Experiment
Lysed smooth (S) cells, separated contents into different types of macromolecules to see transformation ability (only DNA)
Hershey-Chase
Radioactively tagged protein coats and DNA of phages before affecting bacteria with virus (DNA/RNA and protein); conclusion that DNA = genetic info.
Rosalind Franklin
3D structure, helical, 2 strands, consistent width helix, consistent distance between turns, nucleotides stacked like rungs of ladder
Erwin Chargaff
Purines (2 rings) AG = pyrimidines (1 ring) CT, A = T and C = G, A+T does not equal C+G
A and T: 2 bonds, C and G: 3 bonds
Watson and Crick
DNA model explains how it carries genetic information/how info. Is replicated
Double helix with 2 strands held together with H-bonds, sugar-phosphate backbone outside of helix joined by phosphodiester linkages, 4 nitrogenous bases (rungs) attached to backbone with covalent bonds
A/T have 2 bonds, C/G have 3 bonds
Antiparallel in opposite directions (3’ -> 5’ and 5’ -> 3’); complementary; each strand is template and mechanism for DNA replication
3’ end has free OH, 5’ end has free phosphate (for dehydration synthesis)
Purine always pairs with pyrimidine (AT are straight ladders and CG are curved ladders)
Nucleotide structure
Phosphate, sugar (deoxyribose), nitrogenous base, pyrimidines (CT), purines (AG)
DNA replication (check large organizer for transcription/translation)
Semi-conservative replication, each new molecule of DNA has 1 parental strand and 1 newly synthesized strand
Mutation: nucleotide sequence changes in DNA; permanent change in daughter molecule
Evolutionary significance: if in germ cells, mutations can pass onto next generations (source of variation/new alleles)