Download DNA: Deoxyribonucleic acid

TRANSFORMATION
Transformation is the process in which information is moved from one cell to another.
In 1928, Frederick Griffith performed an experiment to show that bacteria are
capable of transferring genetic information through transformation.
GRIFFITH’S EXPERIMENT
PURPOSE OF GRIFFITH’S EXPERIMENT
Griffith was initially looking for a vaccine for pneumonia.
However, when he got the results he started studying transformation of genetic
material.
CONCLUSION OF GRIFFITH’S EXPERIMENT
Griffith concluded that the disease causing bacteria was able to move its information
from one cell to another by a molecule found inside the mouse.
He wasn’t sure what molecule it was exactly but he proved transformation could
happen.
AVERY – MACLEOD – MCCARTY EXPERIMENT
In 1944, the Avery – MacLeod McCarty experiment started.
They also did their study on pneumonia.
PURPOSE OF THE EXPERIMENT
Avery, MacLeod and McCarty wanted to find out which molecule from Griffith’s
experiment contributed to transformation.
They studied the four macromolecules in the human body: carbohydrates, proteins,
lipids and nucleic acids.
EXPERIMENTAL PROCEDURE
Avery and his team purposely injected enzymes into the bacteria that killed each type
of macromolecule individually.
They were looking for the molecule that still allowed transformation to occur.
EXPERIMENTAL RESULTS:
1. Destroyed the Protein – Result: Transformation Occurred
2. Destroyed the Lipids – Result: Transformation Occurred
3. Destroyed the Carbohydrates – Result: Transformation Occurred
4. Destroyed the RNA – Result: Transformation Occurred
5. Destroyed the DNA– Result: No Transformation Occurred
CONCLUSION:
Nucleic Acids (DNA) causes transformation.
AVERY – MACLEOD – MCCARTY EXPERIMENT
HERSHEY – CHASE EXPERIMENT
In 1952, Alfred Hershey and Martha Chase conducted an experiment to confirm that
DNA was indeed the molecule causing transformation.
There was still some debate amongst that scientific community that protein could be
causing transformation instead of DNA.
PURPOSE OF HERSHEY CHASE EXPERIMENT
To test protein and DNA to see which one causes transformation.
EXPERIMENTAL PROCEDURE
Hershey and chase injected a bacteriophage that contains isotopes of Phosphorous –
32 and Sulfur – 35 into the bacteria.
A bacteriophage is a virus that eats bacteria.
They used Phosphorous – 32 because proteins have no phosphorous in them and
Sulfur – 35 because DNA has almost no sulfur in it.
They wanted to see which isotopes would spread into new cells and which one would
not.
EXPERIMENTAL RESULTS
The sulfur did not show up in the new bacteria cells, while the phosphorous did.
Conclusion:
This showed that DNA was causing transformation, not protein.
HERSHEY CHASE EXPERIMENT
GENES
Three things scientists understood about genes back in this time:
1. Can be easily copied.
2. They are passed down from generation to generation.
3. They contain traits.
STRUCTURE OF DNA
1. DNA contains four Nitrogen Bases:
Adenine
Cytosine
Guanine
Thymine
STRUCTURE OF DNA
2. DNA contains a phosphate group.
STRUCTURE OF DNA
3. DNA contains a five carbon sugar called Deoxyribose.
STRUCTURE OF DNA
4. DNA contains Hydrogen Bonds that hold the bases together.
SHAPE OF DNA
The basic shape of DNA is called the Double Helix which was founded by James
Watson and Francis Crick.
Realistically, Rosalind Franklin discovered the shape while studying X-Ray diffraction,
but Watson and Crick received the credit and one the Nobel Prize for it.
CHARGRAFF’S RULE
Erwin Chargraff discovered that the nitrogenous bases Adenine and Thymine ALWAYS
binded together and that Cytosine and Guanine ALWAYS binded together.
(assuming normal circumstances).
This is called Chargraff’s Rule or the Rule of Base Pairing.
PURINES
Adenine and Guanine are known as Purines.
Purines are aromatic organic compounds.
PYRIMIDINES
Cytosine and Thymine are known as Pyrimidines.
These are crystalline organic bases.
PICTURE OF DNA