Dept. of Genetics and Plant Breeding
University of Agricultural Sciences
Dharwad, Karnataka, India, 580005
-DNA Repair Mechanism.
All living organisms contains DNA as genetic material
except virus where RNA is the genetic material.
There are two types of nucleic acids are found in the
cells of all living organisms. These are:
1- Deoxyribonucleic acid
2- Ribonucleic acid
The number of DNA molecules = The number of
chromosome per cell.
In bacteriophages and viruses there is a single molecule
of DNA, which remains coiled and is enclosed in a
The main role of DNA in the cell is the long- term
storage of information.
The DNA segments that carry this genetic information
are called genes.
DNA is found in combination with proteins
forming nucleoproteins or the chromatin
Evidences That DNA Is
The Genetic Material
. The genetic material of any organisms is the substance
that stores information about structure, function and
Development of various characteristics of a living
. DNA was not considered to be the possible genetic
studied Streptococcus pneumoniae ,
apathogenic bacterium causing pneumonia
there are 2 strains of Streptococcus:
- S strain is virulent.
- R strain is nonvirulent.
Griffith infected mice with these strains
hoping to understand the difference between
Transformation Of Bacteria
Two Strains Of Streptococcus
Timothy G ,Standish,2000
- live S strain cells killed the mice.
-live R strain cells did not kill the
-heat-killed S strain cells did not kill
-heat-killed S strain + live R strain
cells killed the mic