Question

Identify two structural features of purines and Pyrimidines

Answer 1

Answer:

The answers are:

Purines:

C. contain four ring nitrogen atoms.

E. contain two heterocyclic rings.

Pyrimidines:

C. contain only two ring nitrogen atoms.

E. contain one heterocyclic ring.

Explanation:

Purines and Pyrimidines are nitrogenous bases which are the building blocks of nucleic acids (DNA and RNA).

Purines are composed by two fused heterocyclic rings, one of them is a 6-ring and the other is a 5-ring. Each ring contains two nitrogen atoms which form part of the ring. Thus, the nitrogen positions in purines are: 1', 3', 7' and 9'. Depending on the functional groups bonded to the two-ring structure, a purine base can be Guanidine (G) or Adenine (A).

The structure of Pyrimidines is a single heterocycle ring wich contains two nitrogen atoms in positions 1' and 3'. Depending of the functional groups, they can be: Cytosine (C), Thymidine (T) and Uracil (U, which is found in RNA).