Topics To be Covered

• The search for genetic material
• Transforming principle
• Biochemical Characterization of Transforming principal:-

The search for genetic material :-

• Mendel found that there are alternative forms of factors-now called genes-that account for variations in inherited characteristics.
• Thomas hunt morgan gave the chromosomal theory of inheritance. He spoke about chromosomes he said that the chromosomes play a very important role in the process of inheritance.
• There is something in chromosomes which gets transmitted from rom one generation to mone another generation.
• Boveri – Sutton propose that chromosomes bear hereditary factors.

Transforming principle

• This experiment was conducted by Fredrick Griffith in 1928.
• Griffith perform his experiment with diplococcus Pneumonia which is responsible for pneumonia in organisms.
• He selected two strains of the bacteria. The one is S-type (have smooth polysaccharide coat) and other R-type (devoid of polysaccharide coat). Polysace
• He injected S-type strain into mice body and found that the mice was dead after. Some time.

Conclusion :-

• In autopsy he found – virulent (s type) and Non virulent (R type).
• Griffith concluded that there was a genetic material in heated S-strains bacteria that transformed R type into virulent S-type. He was not sure about the nature of genetic material whether it was DNA, RNA, carbohydrate or protein please
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Biochemical Characterisation of Transforming principal :-

• Oswald avery, colin macleod and Maclyn mccarty repeated the experiment to identified the biochemical nature of transforming substances.
• They purified biochemical from heated-S strain i.e, protein, RNA, DNA.

Conclusion :-

So they concluded that a genetic material is DNA because in the presence of it transformation takes place not in the presence of RNA, Protein.