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DNA and the CENTRAL
DOGMA
Everything you never wanted to know,
but still need to understand… and then
some more bonus stuff to really make
you happy
Transformation of Bacteria
a) Mouse dies
b) Mouse lives
c) Mouse lives
d) Mouse dies. Living S
cells are found in blood
sample from dead mouse
1928 Fredrick Griffith
Phages are viruses that infect bacteria (bacteriophage)
1. Mix phages
with bacteria
2. Blend to mix
3. Centrifuge
and measure
radioactivity
What makes up
DNA
subunits?
•
5-carbon
sugar
•
Phosphate
•
Nitrogenous
base
• A and G are
Purines (double
rings)
• C and T are
pyrimidines
(single rings)
“Attorney
Generals are
pure”
DNA REPLICATION
2 complimentary
strands. A=T C≡G
Helicase breaks H
bonds and unzips
DNA polymerase
attaches
nucleotides to
each template
strand
Each “daughter”
DNA consists of
one parental and
one new strand
Conservative –
parental helix
remains intact; an
all new copy is
made
Dispersive –
– two strands each strand
separate and
contains pieces
each functions of old and new
as a template DNA
SemiConservative
Meselson-Stahl Experiment
1st
replication
~20 min
2nd
replication
~40 min
Incorporates
heavy nitrogen
into DNA
Incorporates
lighter nitrogen
into DNA
“new” DNA synthesized would
be lighter than the “old” DNA
EUKARYOTES: many origins of
replication
Incorporation of nucleotide
Enzyme DNA
polymerase
catalyzes this
reaction
5’3’ direction of one strand
runs counter to the other
DNA Helicase – unzips
Topoisomerase – unwind DNA
SSBP – single strand binding
proteins, hold strands open
Primase – joins RNA nucleotides
to eukaryotes (primer is required
for polymerase to synthesize)
DNA Polymerase – adds
nucleotides
Ligase – link Okazaki fragments
New
DNA
Excision
repair of
DNA
FROM GENE TO PROTEIN
Beadle and Tatum – one gene, one polypeptide