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Question : (a) state the central dogma as proposed by francis crick are thereany exceptions to it ? Suppport your answer with a reason and an example (b) Explain how the biochemical chraterisation (nature) of Transforming pronciple was determined which was not defined from Griffith 's experiments |
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Answer» Solution :(a) Francis crick proposed the central dogma in molecular biology , which states that the genetic information flows from DNA`rarr`RNBA`rarr`Protein `DNAoverset(transcription)rarrmRNA(overset(translation)rarrProtein` In some viruses central dogma is seen in reverse direction that is from RNA to DNA as RNA is the main genetic material for example : Retro virus (HIV) and the process is reverse tarnscription (b) Tansforming principle : in 1928 fredericlk GRIFFITH INA series of experiments with straptococcus penumonie (bacteriumerepsonsiable for pneumoia) withessed a miraculous transformation in the bacteria during the course of his experiment a living organism (bacteria ) had changed in phyical form He concluded that the R strain bacteria had some how been transformed by the heat killed s strain bacteria some tramforming principle transferredfrom the heat killed s strain had enabled the r strain to sysnthises a smooth polysaccharider coat and become virulent .This must be DUE to the transfer of the genetic material .However the biochemical nature of genetic material was not defined form his experiments They also discovbeed that proteindigensting ENZYMES (proteses) and RNA disgeting enzymes (RNases) did not AFFECT transformation so the transforming substancewas not a protein or RNAdisgestion with inhibit transformation suggestion that the DNA caused the transformation They concluded that DNA is the hereditary material but not all biologist were convinced . |
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