DNA Structure

Intro How do genes work? What are they made of? How do they determine characteristics of organsims? Intro

History People that helped discover DNA Frederick Griffith Rough Bacteria – did not cause pneumonia Smooth Bacteria – caused pneumonia Injected both types into mice, only smooth killed mice He injected bacteria into mice heat-killed bacteria passed their disease causing ability to the harmless strain of bacteria. (called transformation) Transformation – process by which one strain of bacteria is changed by a gene from another strain of bacteria (gene was passed) History People that helped discover DNA

Avery – Discovered that DNA stores and transmits the genetic information from one generation to another History

DNA Genes are made of DNA DNA – stores and transmits genetic information from one generation to the next Huge molecule that is made of nucleotides Nucleotide – monomer of a nucleic acid made of a 5-carbon sugar, and phosphate group, and a nitrogenous base. DNA

Nucleotides Four different nucleotides Purines Pyrimidines Adenine and Guanine Pyrimidines Cytosine and Thymine These molecules are different sizes A purine pairs with a pyrimidine A – T G - C Nucleotides

Backbone(sides of the ladder) of DNA is formed by the phosphate groups and 5- Carbon sugars Bases (A, T, G, C) stick out sideways from the chain (rungs of the ladder) Nucleotides can be in any order or sequence DNA Structure

Double Helix Discovered by Watson and Crick Rosland Franklin Two strands wound around one another Hydrogen bonds hold the two strands together in the middle, between the bases Rosland Franklin helped them discover the “twist” Double Helix

in DNA can only form between adenine and thymine and between cytosine and guanine. A always pairs with T G always pairs with C Given the DNA strand GCTATCGTTA What is the complementary DNA strand? Base Pairing Rules