DNA

DNA Deoxyribose Nucleic Acid DNA is a heredity molecule –passed on from parent/s –generation to generation Stores and transmits genetic information Tells the cells which proteins to make DNA  RNA  Amino Acid  Protein  Trait

History of DNA 1920s Erwin Chargaff figured out that the nitrogen bases existed in pairs

History of DNA Rosalind Franklin took x-ray diffraction photographs of DNA crystals She was first to truly figure out the shape of DNA

History of DNA James Watson and Francis Crick created “model” of DNA –Double Helix –Twisted Ladder –2 sides

The Double Helix Made of repeating units of NUCLEOTIDES(monomer of DNA) Sugar, phosphate, and nitrogen base Nucleotides held together by covalent bonds (strong) Backbone (the two sides): alternating SUGAR and PHOSPHATE Sugar is Deoxyribose Center “rungs” : two nitrogen bases connected by a hydrogen bond (weak)

Nitrogen Bases –Adenine (A) –Guanine (G) –Cytosine (C) –Thymine (T) Complementary Base Pairing Base-pairing rules –Cytosine bonds with Guanine: C-G –Adenine bonds with Thymine: A-T

Why are organisms different? Base Sequence (order of nitrogen bases) are different for every organism The more similar the physical traits then the more similar the DNA sequencing

Pass out picture!

Types of Nitrogen Bases Classified by their “ring” shape Purines –Double ring shape –Adenine and Guanine Pyrimidines –Single ring shape –Cytosine and Thymine

Purine “pairs” with a pyrimidine. A – T C - G