The Masterof

Deoxyribonucleic Acid
DNA
The Master of
Hereditary Material
Learning Outcomes
I will…
- Summarize the discoveries that led to the discovery
of the DNA molecule & its structure
- Describe how genetic information is found in the
bases of DNA
- Describe how DNA is put into chromosomes
- Describe how DNA replicates itself
Graffiti Activity
Read (briefly) through pages 642-650 - you have 10
minutes
Specifically focus on the experiments by certain people
Jot down the important information if you choose to
I will explain how the activity works
In Summary...
Friedrich Miescher
- extracted a white
substance from white
blood cells that he called
nuclein
- Found that nuclein was
composed of an acidic
part (nucleic acid) and an
alkaline part (protein)
In Summary...
-
Joachim Hammerling
Demonstrated that the nucleus was the likely region
that the hereditary information was found
Worked with green algae and would cut off the cap
and feet of cells
Foot contained nucleus so did not regenerate
His results encouraged others to look in the nucleus
for the hereditary material
In Summary...
-
Frederick Griffith
Worked with Streptococcus pneumoniae
S form is smooth and R form is rough
S form is deadly
He injected different mice with these different
strains - S mice died and R mice lived
He heat killed the S strain and injected mice and
they lived.
He heat killed S strain and mixed with living R strain
and found that the mice died when injected
In Summary...
Frederick Griffith
- He concluded that some part of the S strain made it
inside the R strain causing it to become deadly
- This process of DNA from one cell entering another
cell and becoming part of its DNA is called
transformation
In Summary...
-
Avery, MacLeod, McCarty
Built on Griffith’s research
They chemically destroyed the different chemicals in
dead cells to see if it would lose the ability to
transform
When they destroyed polysaccharides (proteins),
fats, and RNA, transformation still occurred
Only when DNase was used to break up DNA did the
transformation stop
Shows that DNA is what holds the hereditary
materials
In Summary...
-
Alfred Hershey and Martha Chase
Worked with E. coli bacteria and bacteriophages
(viruses that target bacteria)
Bacteriophages (phages) have two parts: DNA and
protein coat
Phages inject their DNA into a bacteria and through
transformation incorporates their DNA into their
host
Avery and Chase attached radioactive isotopes to
phages to look for two things - protein and DNA
In Summary...
-
Alfred Hershey and Martha Chase
When they marked the protein and looked at the
cell, the radioactive marker was not found
When they marked the DNA and looked at the cell,
the radioactive marker was now inside of it!
This experiment showed that DNA carried genetic
information
After this experiment, DNA was accepted as the
hereditary material
In Summary...
Watson and Crick
- Discovered the structure of DNA (with help from
many others)
- Rosalind Franklin used x-ray diffraction technology
to take a picture of DNA and Watson and Crick then
took the picture (without permission)
- Erwin Chargaff explained that DNA contained equal
amounts of A and T molecules and G and C
molecules stating that A pairs with T and G pairs with
C
In Summary...
Watson and Crick
- With the helpful information, this team constructed
a 3-D model showing a double helical shape with the
bases in the middle and a phosphate sugar backbone
- They received the Nobel Prize for their discovery
- Franklin was not acknowledged for her contribution
until after her death