Jan. 2016
SCIENTISTS & DNA Discovery
Griffith- “F” he failed!
Used mice to try to find why
the smooth bacteria caused
disease when the rough
bacteria did not.
He thought the smooth
bacteria produced a poison
that did the killing. He was
wrong. He found the rough
(good) bacteria when mixed
with smooth killed (bad)
bacteria, it changed the good
into bad. He failed to find the
“factor” that caused disease,
but did discover
TRANSFORMATION
Change from one thing
into another (good→bad)
Avery – “A” for
DNA!
Also used mice to try to find
the “factor” that bacteria use to
cause disease
Avery tested the proteins,
carbohydrates, lipids, and
nucleic acids of bacteria to find
the “factor” that caused
disease. He found:
DNA
Hershey & Chase
Used BACTERIOPHAGE
(VIRUS) to determine if
the protein coat (CAPSID)
or DNA is injected by the
bacteriophages into bacteria
They determined that it was
the DNA by using
radioactive markers.
HINT: Bacteriophages
CHASE down the bacteria
to inject their DNA.
Rosalind Franklin
Franklin used X-rays of DNA to
discover the shape of DNA which
Watson & Crick stole to create the
DOUBLE HELIX model.
She died of cancer from being
exposed to a lot of x-rays before
being given any credit for her
discovery.
Watson & Crick
Watson & Crick used Rosalind
Franklin’s discovery to create the
DOUBLE HELIX model.
They won the Nobel prize for
creating the first accurate model of
DNA.
Sugar + Phosphate Group
Make the BACKBONE
(sides of ladder) of the DNA
Chargaff
Discovered that:
% Adenine (A) = % Thymine (T)
%Cytosine (C) = % Guanine (G)
Nitrogen bases are held together by
HYDROGEN BONDS
Adenine ==== Thymine (Double Bond)
Cytosine ===== Guanine (Triple Bond)
NUCLEOTIDE
Building block of DNA
(Nucleic Acids)
Consists of 3 things:



Phosphate Group
5-Carbon Sugar
(Deoxyribose)
Nitrogen Base (A, T, C, or G)
Pyrimidines
Thymine and Cytosine
Single Ring Nitrogen
Base
Purines
(P-Urine in the outhouse)
Adenine and Guanine
Double Ring Nitrogen
Base