Meaning of base-pairing rules

base'-pair•ing rules"

Pronunciation: [key]
— Genetics. Genetics.
  1. constraints imposed by the molecular structure of DNA and RNA on the formation of hydrogen bonds among the four purine and pyrimidine bases such that adenine pairs with thymine or uracil, and guanine pairs with cytosine.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.