(a) Why is DNA molecule a more stable genetic material than RNA? Explain.
(b) “Unambiguous”, “degenerate” and “Universal” are some of the salient
features of genetics code. Explain.

OR

(a) Explain the experiment performed by Griffith on Streptococcus pneumoniae. What did he conclude from this experiment?
(b) Name the three scientist who followed up Griffith’s experiments.
(c) What did they conclude and how?

(a) DNA is more stable than those of RNA as it contain less number of hydroxyl groups and it has thymine (5-methyle uracil) in place of uracil which provides it the additional stability.  Ribose sugar is more reactive than deoxyribose sugar, due to presence of a free 2' hydroxyl group which makes it more labile and easily degradable. 
(b) Unambiguous: The genetic code is unambiguous because each triplet specifies only a single amino acid
Degeneracy: The degeneracy of the genetic code refers to the fact that most amino acids are specified by more than one codon. The exceptions are methionine (AUG) and tryptophan (UGG). The degeneracy is found primarily the third position. 

Universal: The genetic  code is nearly universal: for example, from bacteria to human UUU would code for Phenylalanine (phe). Some exceptions to this rule have been found in mitochondrial codons, and in some protozoans.
OR

(a) Griffith perform experiment in which he mixed both form of bacteria that is nonvirulent and virulent form. As a result he find that mice get infected and develops pneumonia and finally died. 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. Heat killed bacteria can be changed to virulent form.
(b) Oswald Avery, Colin MacLeod, and Maclyn McCarty (1933-44).
(c) Transformation occur due to DNA.