base pairing

The specific association between two complementary strands of nucleic acids that results from the formation of hydrogen bonds between the base components of
the nucleotides of each strand: A=T and G=C in DNA, A=U and G=C (and sometimes G=U) in RNA (the lines indicate the number of hydrogen bonds). Single-stranded nucleic acid molecules
can adopt a partially double-stranded structure through intrastrand base pairing.