Experiment # 1
Does the disease causing bacteria produce a poison?
Mouse LivedInjected into
Summary: The mouse lived, this suggests that disease
causing bacteria (smooth) does not release a chemical poison.
Experiment # 2
Summary: By themselves neither should of made the mice sick,
however, many of the mice got pneumonia and died. The lungs
of the mice were filled with the disease causing bacteria.
These experiments showed that one strain of bacteria
could be transformed into another type of bacteria.
Griffith hypothesized that when the live, harmless
bacteria and heat killed bacteria were mixed, some
factor was transferred from the heat killed cells
into the live harmless cells. This factor may contain
“information” that could transform the harmless
This was the first evidence that DNA stores and
transmits genetic information.
Oswald Avery - 1944
Oswald Avery led a group of scientists to further
investigate the work of Griffith. They wanted find out which
molecule in the heat killed bacteria was the most important
Edwin Chargaff – 1947
Studied DNA in various species
Nitrogen bases are proportionate within a species
Ratio of bases are various between species
•Adenine and Thymine were found in proportionate amounts
•Cytosine and Guanine were found in proportionate amounts
Alfred Hershey and Martha Chase -1952
Their experiments concluded that the genetic material
of the bacteriphage was DNA and not protein.