Title: DNA The Language of Life
Intro: Scientists identified DNA as a chemical in the nucleus of the cell more than
100 years ago. However, Mendel, Morgan, … accomplished all their work on genetics
without understanding how DNA worked. This was not understood until many years
later. The following describes some of the important research that have taught us
about the structure and function of DNA.
1- Griffith’s “Transforming Factor” is the genetic material
a- 1928 Frederick Griffith was studying two forms of pneumonia, one
harmless in mice and the other fatal
bcd- When he injected the harmless with the heat treated strain the mice died.
Neither strain should have killed the mice he expected them to live
e-
fg- All the descendants of the killed bacteria were also deadly, they inherited
the gene
hiJ- Drawing
2- Oswald Avery – The “Transforming Factor” is DNA
a- Scientists still wanted to know if the transforming factor was DNA or
protein
b- 1944 Oswald Avery expanded on Griffiths model
cde-
fg- Avery concluded that DNA was the genetic material of the cell.
3- Viruses provide additional evidence
a- Scientists were still skeptical that DNA was the inherited material. DNA
has only 4 nucleotides and many people thought that this made it much to
simple to account for all the genetic variation seen in organisms
b- 1952 – Alfred Hershey and Martha Chase conducted a series of
experiments on viruses
1- A virus is a packet of genetic information with protein wrapped
around it
234-
c- Hershey and Chase new that the phage they were working with had DNA
on the inside and a protein coat on the outside. They devised an
experiment to determine if it was the DNA or the protein entering the cell
and directing the host cells activity to make new phages
12345678- They concluded that the phages DNA had entered the cell during the
infection but that proteins did not Therefore they concluded that the DNA
must be the genetic material responsible for producing new pahges
9- Diagram