Complementary deoxyribonucleic acid (DNA) is DNA produced from RNA through reverse transcription, a process that involves cooperation between several different enzymes. This differs from the usual reproduction of genetic material in a cell, where enzymes work to turn DNA into RNA for the purpose of building proteins to assist with cell functions. The body uses complementary DNA, also known as cDNA, in a number of different ways. It is also very important for researchers.
In the process of creating complementary DNA, the body uses an enzyme called reverse transcriptase, along with DNA polymerase. The complementary DNA copies a region of a strand, and does not generate a complete copy of someone's DNA. The replication process turns chains of RNA into DNA strands, encoding the genetic material in a new format. Retroviruses take advantage of this to create more copies of themselves, allowing the copies to circulate through the body.
One use for complementary DNA comes up in scientific research. Researchers who want to turn RNA into DNA can catalyze this process in culture to develop copies of DNA. This can be useful for the manipulation of genetic material, where a researcher may need to work with DNA or have a preference to do so. The conversion between RNA and DNA can also provide important information about what a strand of DNA does and how it works.
This term can also refer to a single strand of DNA that pairs with another, fitting the sets of base pairs together like a zipper. This can be useful when researchers need large numbers of cloned copies of DNA. They can use a technique called polymerase chain reaction (PCR) to separate double-stranded DNA, and encourage each half to create a complementary copy to generate two new sets of DNA. Each set can be encouraged to divide and copy again, until the researcher has enough copies of the DNA of interest to work with.
One important use for PCR and complementary DNA is in the investigation of limited genetic material, like blood from a crime scene. The blood may not provide enough information as is to be useful in an investigation or in court. Using PCR, a technician can amplify the DNA to make more copies available for testing and research. PCR is also important in physical anthropology, where it can offer an opportunity to study the genetic code of earlier humans, using fragments successfully copied with PCR techniques.