Frederick GriffithBy: Lexie Smathers and Claire Smith

About GriffithCredited for the discovery of bacteria containing a molecule that helped transfer DNA from one cell to

another

Motivation? –trying to discover how bacteria made people sick

Griffith’s Experiment

First, he injected mice with disease-causing bacteria (S-strain)- they died of pneumonia.

Next, he injected mice with harmless bacteria (R-strain) - they lived.

He then killed the S-strain with heat. When he injected the mice with this, there was no harm caused.

Then he mixed the dead S-strain and the alive R-strain, which, combined, caused a concoction that gave the injected mice pneumonia.

The disease-causing bacteria were found in the lungs

Overall conclusion: heat-killed bacteria had passed their disease-causing ability to the harmless bacteria

TransformationTransformation- one type of bacteria (harmless bacteria) had been changed permanently into another (disease-causing form)

This transforming factor had to be a gene because the ability to cause the disease was inherited by the offspring of the transformed, or harmless, bacteria

Contributions To Other Scientist’s

FindingsOswald Avery contributed to Griffiths’ overall conclusion after performing an experiment that showed which molecule wouldn’t allow transformation to occur if it weren’t there, he discovered DNA was the transforming factor

Alfred Hershey and Martha Chase used radiation from phosphorus and sulfur to confirm Avery’s results. Therefore, backing up Griffith’s experiment.

Overall, Griffith’s experiment was so

important that, even 24 years after it occurred, people were still make

contributions to it.

Resources:http://en.wikipedia.org/wiki/Frederick_Griffith

Miller & Levine Biology Book

http://en.wikipedia.org/wiki/File:SalmonellaNIAID.jpg