Base pair

In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called base pair. As DNA is usually double-stranded, the number of base pairs in the dsDNA strand equals the number of nucleotides in one of the strands. In DNA, adenine and thymine, as well as guanine and cytosine, can be a base pair. In RNA, thymine is replaced by uracil.