the discovery of dna
DESCRIPTION
The Discovery of DNA. GREGOR MENDEL. 1847 Austrian monk who worked with pea plants to study genetic inheritance “Father of Genetics” Discovered ‘factors’ are passed down from parent to offspring *Did NOT know what DNA was or that it was the genetic material. FREDERICK GRIFFITH. 1928 - PowerPoint PPT PresentationTRANSCRIPT
The Discovery of DNA
GREGOR MENDEL1847Austrian monk who worked
with pea plants to study genetic inheritance
“Father of Genetics”Discovered ‘factors’ are
passed down from parent to offspring
*Did NOT know what DNA was or that it was the genetic material
FREDERICK GRIFFITH1928Griffith's experiment involved mice and two types of
pneumonia, a virulent (S) and non-virulent kind (R).S = smooth coated bacteriaR = rough (no coating) bacteria
EXPERIMENT:Injected live S = mouse diedInjected live R = mouse livedInjected heat killed S = mouse livedInjected heat killed S + live R = mouse died
Cells inside dead mouse had S bacteria CONCLUSION * genetic material must have been transferred
from heat killed S bacteria to live R bacteria changed harmless R bacteria into deadly S bacteria =
“transformation principle”
OSWALD AVERY1942Continued Griffith’s experiment
to see what the genetic material was that was being passed on.
Experiment - he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the virulent pneumonia. Transformation still occurred.
Next he destroyed the deoxyribonucleic acid. Transformation did not occur. DNA must be inherited material
NOW THAT WE KNOW DNA IS THE GENETIC MATERIAL… WHAT IS IT’S STRUCTURE?
HERSHEY AND CHASE1952Proteins or DNA = genetic
material?Worked with
bacteriophage:Infects bacteria cells Composed of protein coat
with DNA insideUsed radioactive isotopes
to “tag” DNA and proteins Helped confirm DNA is
genetic material
ERWIN CHARGAFF1940Snoticed a pattern in the
amounts of the four bases: adenine, guanine, cytosine, and thymine.
took samples of DNA of different cells and found that the amount of adenine = amount of thymine, and that the amount of guanine = equal the amount of cytosine. CHARGAFF’S RULE: A=T and G=C
ROSALIND FRANKLIN1952Decided to try to make a
crystal of the DNA molecule to obtain an x-ray of it
They were successful x-ray crystallography image of DNA
The image appeared to contain rungs, like those on a ladder between to strands that are side by side.
It showed DNA had a (X) helix shape.
WATSON AND CRICK1953Co-discoverers of the
structure of DNA Used x-ray diffraction images
from Rosalind Franklin and proposed the double helix structure of DNA
Built the first 3D model of DNA