1.
Explain the structural differences between Cytosine, Uracil, and Thymine.
Solution
Uracil : It is a pyramidine base that only occurs in RNA. Its heterocyclic aromatic ring contains
two keto groups at its C-2 and C-4 position. Its molar mass is 112.0868 g/mol.
Thymine : It is a pyramidine base that only occurs in DNA. Its heterocyclic aromatic ring
contains two keto groups at C-2 and C-4 group and a methyl group at C-5. Its molar mass is
126.1133g/mol
Cytosine : It is a pyra midine derivative that is found in DNA and RNA. It has a keto group at
C-2 position and an amine group at C-4 position. Its molar mass is approx. 111g/mol.