Short Answer TypeState the ‘Central dogma’ as proposed by Francis Crick. Are there any exceptions to it? Support your answer with a reason and an example.
Explain how the biochemical characterisation (nature) of ‘Transoforming Principle’ was determined. which was not defined from Griffith’s experiments.
Transforming Principle :
In 1928, Frederick Griffith, in a series of experiments with Streptococcus pneumoniae (bacterium responsible for pneumonia), witnessed a miraculous transformation in the bacteria. During the cource of his experiment, a living organism (bacteria) had changed in physical form.
He concluded that the R strain bacteria had somehow been transformed by the heat - killed S strain bacteria. Some ‘transforming principle’, transferred from the heat-killed S strain, had enabled the R strain to synthesise a smooth polysaccharide coat and become virulent. This must be due to the transfer of the genetic material. However, the biochemical nature of the genetic material was not defined from his experiments.
Oswald Avery, Colin MacLeod and Maclyn McCarty worked to determine the biochemical nature of ‘tranforming principle’ in Griffith’s experiment.
They purified biochemicals (proteins, DNA, RNA, etc.) from the heat-killed S cells to see which ones could transform live R cells into S cells. They discovered that DNA alone from S bacteria caused R bacteria to become transformed.
They also discovered that protein - digesting enzymes (proteases) and RNA - digesting enzymes (RNases) did not affect transformation, so the transforming substance was not a protein or RNA. Digestion with DNase did inhibit transformation, suggesting that the DNA caused the transformation.
They concluded that DNA is the hereditary material, but not all biologist were convinced.
Multiple Choice QuestionsWhich of the following is required as inducer(s0 for the expression of lac operon?
galactose
lactose
lactose and galactose
lactose and galactose
The two polypeptides of human insulin are linked together by
phosphodiester bonds
covalent bonds
disulphide bridges
disulphide bridges
Which one of the following is not applicable to RNA?
Complementary base pairing
5, phosphoryl and 3' hydroxyl ends
Heterocyclic nitrogenous bases
Heterocyclic nitrogenous bases
Identify the correct order of organisation of genetic material from largest to smallest
Chromosome, gene, genome, nucleotide
Genome, chromosome, nucleotide, gene
Genome, chromosome, gene, nucleotide
Genome, chromosome, gene, nucleotide
Balbiani rings rigs are sites of
Lipid synthesis
Nucleotide synthesis
Polysaccharide synthesis
Polysaccharide synthesis
Satellite DNA is important because it
codes for proteins needed in cell cycle.
shows high degree of polymorphism in population and also the same degree of polymorphism in an individual, which is heritable from parents to children.
does not code for proteins and is same in all members of the population.
does not code for proteins and is same in all members of the population.
Which one of the following shows coiled RNA stands and capsomeres?
Polio virus
Tabacco mosaic virus
Measles virus
Measles virus
Switch
