Molecular Basis of Inheritance – Solutions

1. Group the following as nitrogenous bases and nucleosides:Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

 Solution:

Nitrogenous bases among the group are adenine, thymine, uracil and cytosine. Nucleosides are cytidine and guanosine.

2. If a double stranded DNA has 20 per cent of cytosine, calculate the % of adenine in the DNA.

Solution:

According to Chargaff’s rule, a r-standed DNA molecule contains an equal ratio of purines (adenine and guanine) and pyrimidines (thymine and cytosine). As adenine pairs with thymine, and guanine with cytosine the % of adenine will be equal to the % of thymine, and the % of guanine equals the % of cytosine in a double-stranded DNA.