Experiments that led to the discovery of DNA

Spark notes Edition

Griffith

Experiment:1. S strain bacteria injected into mouse -> mouse died 2. R strain bacteria injected into mouse -> mouse lived3. Heated S strain injected into mouse -> mouse lived4. Heated S (dead) and alive R strain ->mouse died

Outcome: Cells contain a substance called transforming factor that can change the genome of a host.

AveryExperiment:1. S strain bacteria injected into mouse -> mouse died 2. R strain bacteria injected into mouse -> mouse lived3. Heated S strain injected into mouse -> mouse lived4. Heated S (dead) and alive R strain ->mouse died

Outcome: When the S strain was heated and killed its DNA was incorporated into the R strains DNA and changed the R strain into S strain.

*Still unknown whether DNA or protein was the “transforming factor”

Hershey-ChaseExperiment:

Outcome: DNA NOT proteins were the source of genetic material. DNA is the “transforming factor”