DNA The Genetic Material Identifying the Genetic Material

DNA: The Genetic Material

Identifying the Genetic Material n Experiments of Griffith and Avery yielded results that suggested DNA was genetic material (1944)

n Hershey & Chase used the bacteriophage T 2 and radioactive labels to show that virus genes are made of DNA, not protein (1952)

n DNA stores information that tells cells which proteins to make and when to make them

The Structure of DNA n Discovered by Watson & Crick in 1953 & received Nobel Prize in 1962 along with Maurice Wilkins

n n n DNA Polymer : Nucleotide Monomer Each Nucleotide has 3 parts: 1) 5 carbon sugar Deoxyribose 2) Phosphate group PO 4 3) Nitrogen Base

Nitrogen Bases Purines Adenine Guanine Pyrimidines Thymine Cytosine

A T Human 30 30 Plant 27 27 Virus 21 22 n DNA forms a spiral ladder Double Helix n Double helix is held together by weak Hydrogen bonds n Erwin Chargaff Discovery Chargaff’s Rule A=T, G=C G 19 22 28 C 19 22 27

DNA Replication n n Phase of Cell Cycle? Why replicate? Step 1: DNA Helicase unzips DNA by breaking weak Hydrogen bonds. Step 2: DNA polymerase adds nucleotides to exposed nitrogen bases. Step 3: Two DNA molecules form that are identical to original.

n n DNA is referred to as “Semi-conservative”, Each DNA molecule 1 template & 1 new strand DNA polymerase proofreads DNA during its replication so that very few errors occur

n Eukaryotes