Download Lecture Chpt. 16 DNA 1

Chpt. 16
Molecular
Basis of
Inheritance
1920’s
Traits are inherited on
1920’s
But what
makes up
the genetic
material??
DNA or
1928 Fredrick Griffith
Research organism:
Streptococcus
Two strains:
Pathogenic (S)
Harmless (R)
S = :-(
R = :-)
+
h
e
a
t
+
h
e
a
t
:-)
+
+
+
:-(
+
Something from the
dead cells, caused
the good cells to
change into bad
Transformation
We now know
transformation to
be the
assimilation of
DNA by a cell…
Transformation
You will do this in
AP Bio lab #6B
Transformation
1944 Oswald Avery
What was transforming
Hershey
& Chase
1952
Hershey
& Chase
1952
How did this virus
reprogram its host?
Made of
only:
Protein &
DNA
1952 Hershey & Chase-->
*“tagged” 2 parts of
bacteriophage - protein (w/ S) and
DNA (w/ P).
1952 Hershey & Chase-->
*Radioactive phosphate found
inside phage.

DNA IS GENETIC MATERIAL
NOT PROTEIN!!
Picture Proof
Erwin Chargoff 1947
- Bases are
present in a
characteristic ratio.
A:T C:G
•N
•DNA ratio
varies
from species to
species.
A,
T,
G,
C
PURINES
two
organic
PYRIMIDINES
one organic
ring
James WATSON
&
Francis CRICK
Rosalind Franklin
http://www.pbs.org/wgbh/nova/p
hoto51/
Structure of
DNA??
DNA
Backbone
• Polymer of sugarphosphate.
• 2 backbones
present.
DNA
Backbone
• Polymer of sugarphosphate.
• 2 backbones
present.
Nitrogen
Bases
• Bridge the
backbones together.
• Purine +
Pyrimidine = 3 rings.
• Constant distance
between the 2 backbo
• Held together by
H-bonds.
Two H bonds
Three H bonds
10
base
pairs per
twist.
A=T
G C
2 H bonds A:T
3 H-bonds G:C
www.perfectdna.com/products.htm
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
DNA ART
http://www.dna11.com/
“It has not escaped
our notice that the
specific pairing we
have postulated
immediately suggests
a a possible copying
mechanism for genetic
Dear mama and papa,
you are nice I like you
I like Christmas. I cant
wait to see you. LOVE
Erica (and Will.) Ages 6
and 8.