What is complementary base pairing?

Hint: Complementary base pairing is very important in DNA molecule because it allows the base pairs to be arranged in the more energetically favourable way. it is essential in forming the double-helical structure of DNA. It is also important in replication of DNA as it allows semiconservative replication.

Complete answer:
There are chemical cross-links between the two strands in DNA, formed by pairs of nucleotide bases. They always pair up in a particular way, called complementary base pairing or Chargaff’s rule.

Complementary base pairing is the phenomenon where in DNA, guanine always binds to cytosine and adenine always binds to thymine. Guanine and cytosine share three hydrogen bonds while adenine and thymine always share two hydrogen bonds. RNA replaces thymine (T) with a different pyrimidine base called uracil (U).

Complementary base pairing of DNA strands in a double-helix makes it possible to use one strand as a template to construct the other. Only some of the nitrogenous bases of DNA can interact with each other to form a stable DNA molecule.

Additional Information:
- Erwin Chargaff found that in DNA molecules, the ratio of guanine (G) to cytosine (C) and adenine (A) to thymine (T) are equal.
- Human genome is made up of approximately 3 billion base pairs and it is very much complex, because of this we always measure base pairs in Kbp (Kilobase pairs).

Note: This principle of complementary base pairing plays an important role in DNA replication, setting the foundation of heredity by explaining how genetic information can be passed from one generation to another. Complementarity is also utilized in the DNA transcription process, which generates an RNA strand from a DNA template.