question_answer

Identify the given structures and choose the correct combination.

A)  A - Uracil; B - Cytosine                       

B)  A - Cytosine; B ? Uracil

C)  A - Thymine; B - Cytosine                     

D)  A - Thymine; B ? Uracil

Correct Answer: B

Solution :

Cytosine is a pyrimidine derivative discovered by Albert Kossel in 1894 when it was hydrolysed from calf thymus tissue. Uracil another pyrimidine derivative is replaced by thymine in DNA. It was discovered in 1900 isolated by hydrolysis of yeast nuclein. The difference between thymine and uracil is that thymine has a methyl group \[C{{H}_{3}}\] instead of hydrogen at 5?C position.