Page "Complementary DNA" Paragraph 16

Complementary DNA is often used in gene cloning or as gene probes or in the creation of a cDNA library.

When scientists transfer a gene from one cell into another cell in order to express the new genetic material as a protein in the recipient cell, the cDNA will be added to the recipient ( rather than the entire gene ), because the DNA for an entire gene may include DNA that does not code for the protein or that interrupts the coding sequence of the protein ( e. g., introns ).

Partial sequences of cDNAs are often obtained as expressed sequence tags.