(a) State the 'Central dogma' as proposed by Francis Crick. Are there any exceptions to it? Support your answer with a reason and an example.
(b) Explain how the biochemical characterisation(nature) of "Transforming Principle" was determined, which was not defined from Griffith's experiments.
(b) Explain how the biochemical characterisation(nature) of "Transforming Principle" was determined, which was not defined from Griffith's experiments.
a) During expression of a protein-coding gene, information flows from DNA→ RNA→protein. This directional flow of information is known as the central dogma of molecular biology. It was proposed by Francis Crick. Retroviruses are the exception to central dogma as they transcribe RNA to DNA by the use of a special enzyme called reverse transcriptase.
b) Griffith performed experiments with the bacteria Streptococcus pneumonia. This bacterium has two strains − S strain and R strain. S strain produces smooth colonies on the culture plate, have a polysaccharide coat and was virulent (causes pneumonia). R strain produce rough colonies on the culture plate, do not have a polysaccharide coat and was non-virulent (does not cause pneumonia). It was observed that live R strain in the presence of heat-killed S strain produces virulence because somehow R strain bacteria are transformed by heat-killed S strain bacteria. Hence, it was concluded that there must be the transfer of genetic material.
a) During expression of a protein-coding gene, information flows from DNA→ RNA→protein. This directional flow of information is known as the central dogma of molecular biology. It was proposed by Francis Crick. Retroviruses are the exception to central dogma as they transcribe RNA to DNA by the use of a special enzyme called reverse transcriptase.
b) Griffith performed experiments with the bacteria Streptococcus pneumonia. This bacterium has two strains − S strain and R strain. S strain produces smooth colonies on the culture plate, have a polysaccharide coat and was virulent (causes pneumonia). R strain produce rough colonies on the culture plate, do not have a polysaccharide coat and was non-virulent (does not cause pneumonia). It was observed that live R strain in the presence of heat-killed S strain produces virulence because somehow R strain bacteria are transformed by heat-killed S strain bacteria. Hence, it was concluded that there must be the transfer of genetic material.
