PROOF AND EXPERIMENTS FOR RNA AS GENETIC MATERIAL

2. RNA
 Ribonucleic acid (RNA) is
a polymeric molecule
essential in various
biological roles
in coding, decoding,
regulation and expression
of genes

3. SOMEORGANISMSHAVERNAASGENETIC
MATERIAL:
 SomeViruses have RNA as Genetic Material.
 RNAVirus ( RiboVirus ) may have ssRNA or
dsRNA enveloped by Protein Coat.
 Human diseases caused by RNA viruses include
 SARS, Influenza ,Hepatitis C, Measles, Mumps
and Rabies
 Rous SarcomaVirus (causing cancer ) and HIV
(causing AIDS) both are Retrovirus using Reverse
Transcription for DNA synthesis in host cell

4. EXAMPLESOFPLANTRNAVIRUSES
 Tobacco MosaicVirus (TMV ) was crystallized
by Stanley (1935) for the first time
 TMV causesTobacco mosaic disease .
 TMV can also cause disease inTomato,
Pepper, Snapdragon and Marigold .
 Papaya Ring Spot virus (PRV)
 Potato Leaf RollVirus (PLRV)

5. RNAVIRUSES
TMV HIV HEPATITES C
VIRUS

6. EVIDENCEINFAVOUROFRNAAS
GENETICMATERIAL:
 The first evidence that RNA also has
the capacity to carry genetic
information came from experiments
conducted with tobacco mosaic
virus (TMV).

7. This virus does not
contain any DNA,
and is composed of
RNA (6%)
surrounded by a
hollow cylinder of
protein subunits.

8. Experimentswithtobaccomosaicvirus(TMV)
 A Gierer and G Schramm ( 1956 ) when
inoculated tobacco plants with Purified RNA
isolated fromTMV - Lesions appeared on
leaves of healthy plant .
 The experiments conducted by
H. Fraenkel-Conrat in California showing
that RNA is the genetic material in this
virus.

9.  Techniques were first developed for separating
TMV particles into RNA and proteins.
 Later by using RNA and proteins separately in
tests for infectivity, it could be shown that RNA
alone was able to cause infection. Such a property
was not found in the protein fraction .

10.  Fraenkel-Conrat and Singer took two
different strains ofTMV and
separated the RNAs from protein
coats, reconstituted hybrid viruses by
mixing the proteins of one strain with
the RNA of the second strain, and vice
versa.

11. Reconstruction of virus, showing that reconstructed
virus gives progeny which resembles the virus from
which RNA was derived

12. Inoculated HybridTMV into healthy
tobacco plant -Tobacco Mosaic disease
appeared.
TMV progeny isolated from diseased
plant showed parental RNA only but
not parental proteins.
This provided evidence that RNA
carries information for assembly of
Virus particles and not proteins

13. RNA thus is the Genetic Material
in TMV