DNA: The Chemical Nature of the Gene CHAPTER 10 DNA: The Chemical Nature of the Gene

Key characteristics of the genetic material Store information Replicate faithfully Encode the phenotype - Stable - Undergo change

Early studies of DNA Nucleus contained material that was slightly acidic and rich in phosphorus – Miescher called it nuclein; later renamed nucleic acid DNA contains four nitrogenous bases – adenine, cytosine, guanine, and thymine DNA made up of linked repeating units, called nucleotides; each nucleotide contains a sugar, a phosphate, and a base

Chargaff’s rules: in DNA, the amount of adenine is always equal to the amount of thymine (A = T), and the amount of guanine is always equal to the amount of cytosine (G = C)

DNA as the genetic material – evidence from experiments with bacteria and their viruses

Discovery of the transforming principle Griffith – 1928 Experiments with Streptococcus pneumoniae

Identification of the transforming principle Avery, MacLeod, and McCarty - 1944

The Hershey-Chase experiment – E. coli and phage T2

Structure of DNA – Watson and Crick’s model

RNA as genetic material

Primary structure of DNA and RNA – sequence of nucleotides joined together by phosphodiester linkages Each nucleotide made of a sugar, a phosphate, and a base

Secondary structure of DNA The double helix

The central dogma

Special structures can form in DNA and RNA Hairpin

Stem

Secondary structure of RNA component of RNase P of E. coli