The Structure of DNA

The Structure of DNA

DNA: The Genetic Material

• The instructions for inherited traits are called genes

• DNA: primary material that causes recognizable, inheritable characteristics in related groups of organisms

Discovering DNA’s Structure

• Griffith (1928)– Discovered that harmless bacteria could cause disease

when they were mixed with killed disease-causing bacteria– Transformation

Discovering DNA’s Structure• Avery (1940’s)– DNA is responsible for transformation in bacteria

Discovering DNA’s StructureHershey & Chase (1950’s)• Showed that DNA, not protein, is the genetic material in

viruses

Discovering DNA’s Structure• Chargaff (1949) showed the base pairs of DNA– Adenine with Thymine– Cytosine with Guanine

Discovering DNA’s Structure• Rosalind Franklin and Maurice Wilkins (1950’s) used x-ray

diffraction to determine the structure of DNA– Images suggested DNA resembled a tightly coiled helix

composed of two chains of nucleotides

Discovering DNA’s Structure

• Watson and Crick (1950’s) constructed a 3D model of DNA– Using information from

past experiments determined the DNA was a double helix

– Won Nobel Prize in 1962

The Shape of DNA

• A DNA molecule looks like a spiral staircase

• Composed of two parallel strands of linked subunits called nucleotides

The Shape of DNA• A nucleotide has 3 parts:

phosphate group, sugar (deoxyribose), and a base

• The phosphate and sugar link together to form the back bone

• The bases pair together to connect the two strands

Base Pairs