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Question
Strongest evidence that DNA is genetic material comes from
Strongest evidence that DNA is genetic material comes from
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Solution
The correct option is B Transformation of bacterial cells.
For any molecule to be genetic material it should have the required properties:1. It must have the information to control the synthesis of enzymes and proteins within a cell. 2. It should self replicate. 3. It should undergo mutations. 4. It must be located in chromosomes. DNA fulfils these properties.But the strongest and the first experimental evidence that DNA is the genetic material came from Transforming principle experiment.The transformation was discovered by Frederick Griffith in 1928 in bacteria Diplococcus pneumoniae. He selected two different strains of these bacteria. S-strain: Smooth surfaced capsulated bacteria pathogenic or virulent to most animals; R strain : rough surfaced non capsulated non virulent. S-strain bacteria injected into mice, mice died. When R strain bacteria was injected into mice, mice lived. Heat killed S-strain injected into mice, mice lived. When a mixture of heat killed S strain and live R strain was injected, mice died. And from this dead mice living S bacteria was recovered. He concluded that the R-strain bacteria had somehow been transformed by the heat killed S-strain bacteria. Some 'transfoming principle transferred from the heat killed S strain had enabled the R strain to synthesize a smooth polysaccharide coat.This must be due to the transfer of genetic material. Later it was found that this genetic material is DNA.
For any molecule to be genetic material it should have the required properties:
1. It must have the information to control the synthesis of enzymes and proteins within a cell.
2. It should self replicate.
3. It should undergo mutations.
4. It must be located in chromosomes. DNA fulfils these properties.
But the strongest and the first experimental evidence that DNA is the genetic material came from Transforming principle experiment.The transformation was discovered by Frederick Griffith in 1928 in bacteria Diplococcus pneumoniae. He selected two different strains of these bacteria. S-strain: Smooth surfaced capsulated bacteria pathogenic or virulent to most animals; R strain : rough surfaced non capsulated non virulent. S-strain bacteria injected into mice, mice died. When R strain bacteria was injected into mice, mice lived. Heat killed S-strain injected into mice, mice lived. When a mixture of heat killed S strain and live R strain was injected, mice died. And from this dead mice living S bacteria was recovered. He concluded that the R-strain bacteria had somehow been transformed by the heat killed S-strain bacteria. Some 'transfoming principle transferred from the heat killed S strain had enabled the R strain to synthesize a smooth polysaccharide coat.This must be due to the transfer of genetic material. Later it was found that this genetic material is DNA.
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