Question

a nitrogenous base in DNA

Answer 1

there are 4 nitrogenous base in dna that are adnenine(A) ,guanine(G) ,cytosine(C) and thymine(T)

Answer 2

there are two main nitrogen bases in DNA
purine and pyridines
Purine = Adenine and Guanine
Pyridines = Cytosine and Thymine

The nitrogen bases project at right angle to this back- bone of phosphate -sugar -phosphate .
since there are two strands of DNA , Nitrogen bases of two strands lie opposite to each other and develop hydrogen bond between them