base-pairing rules

American  

plural noun

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.

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Usage

What are base-pairing rules? Base-pairing rules are the principles that govern which nitrogen bases (or nucleobases) bind together in DNA and RNA structures. A nitrogen base is a molecule that contains nitrogen and has the properties of a base (a kind of organic compound). In this case, the word rule just refers to a certain pattern that nitrogen bases tend to follow. There are five bases that make up DNA and RNA strands: adenine, thymine, cytosine, guanine, and uracil. The rules state that adenine always pairs with thymine (or uracil in RNA) and that cytosine always pairs with guanine. Each base in a pair is called a complementary base: adenine and cytosine are complementary bases and cytosine and guanine are complementary bases.