text: what is a nitrogen base?   a nitrogen base is a base primarily composed of nitrogen.  in the dna ladder-like format, there are 4 rungs.  the rungs are formed from two nitrogen bases that connect in the middle of the rung.  these are the four nitrogen bases according to what nitrogen bases they connect to. they connect to no other, except in rna.  adenine - thymine guanine - cytosine  you can also remember atgc, just as initials to remind you.