Page 4 - CH6 (1)

○ Non­histone chromosomal proteins − Additional set of proteins
required for packaging of chromatin at higher level

Transforming principle, Hershey and Chase experiments, &
Properties of genetic material

Discovery of DNA as a Genetic Material

● Though principles of inheritance and discovery of chromosomes in

nucleus were achieved long time back, there was confusion about
which molecule acted as genetic material.

Transforming Principle

● Griffith performed experiments with the bacteria ​treptococcus
S
.
pneumoniae​This bacterium has two strains − S strain and R strain.

S strain Bacteria R strain Bacteria

○ Produce smooth colonies on ○ Produce rough colonies on
culture plate culture plate

○ Have a polysaccharide coat ○ Do not have a

polysaccharide coat

○ Virulent (causes ○ Non­virulent (does not cause
pneumonia) pneumonia)

● Griffith’s experiment