DNA, AND IN SOME CASES
RNA, IS THE PRIMARY SOURCE
OF HERITABLE INFORMATION
Genetic Info is transmitted from one generation to the
next through DNA or RNA
Genetic Information

Info is stored in and
passed to subsequent
generations through
DNA molecules and, in
some cases, RNA
molecules
 Where
is it stored?
 Nitrogen
 How
bases
is it passed on?
 Mitosis
and/or Meiosis
Types of Chromosomes
Eukaryotic

Multiple linear
chromosomes
Noneukaryotic

Circular Chromosomes
Plasmids


Prokaryotes, viruses
and eukaryotes can
contain plasmids
Plasmids are small
extra-chromosomal,
double-stranded
circular DNA molecules
Proof that DNA is the carrier of
genetic information…
The discovery of the
genetic role of DNA
began with the
research of Fredrick
Griffith in 1928.
Griffith worked with 2
strains of bacterium,
one pathogenic
(SMOOTH) and one
harmless (ROUGH)
When he mixed heatkilled remains of the
pathogenic strain with
living cells of the
harmless strain, some of
the living cells became
pathogenic.
He called this
phenomenon
Transformation, now
defined as a change in
genotype and
phenotype due to
assimilation of foreign
DNA.
Proof that DNA is the carrier of
genetic information…
In 1944, Oswald
Avery, Maclyn
McCarty, and Colin
MacLeod announced
that the transforming
substance was DNA
based on their
extension of Griffith's
study.
They treated heat
killed smooth bacteria
to destroy 1.
carbohydrates 2. lipids
3. Proteins 4. RNA 5.
DNA
They mixed each
treatment with live
rough
The only treatment that
did not transform was
5 – DNA- proving DNA
is the transforming
agent
Many biologists
remained skeptical.
Proof that DNA is the carrier of
genetic information…
In 1952, Alfred
Hershey and
Martha Chase
preformed
experiments
showing that DNA is
the genetic material
of a phage known
as T2.
They designed an
experiment showing
that only one of the
two components of
T2 (DNA or protein)
enters an E. coli cell
during infection.
They concluded that
the injected DNA of
the phage provides
the genetic
information.
Proof that DNA is the carrier of
genetic information…
Watson and Crick used
X-ray diffraction
photos from Franklin
and Wilkins to conclude
that DNA is made up of
two antiparallel sugarphosphate backbones.
They determined that
the two strands of DNA
are antiparallel nature
of DNA - the strands
run in opposite
directions. One strand
runs 3' to 5' while the
second strand runs 5' to
3'.
They used Chargaff’s
rule to determine that
the nitrogen bases
connected the two
strands of DNA Adenine binds to
Thymine while Guanine
binds to Cytosine.