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How does reverse transcriptase make complementary DNA from messenger RNA?

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DNA extraction and recombinant DNA technology — recombinant DNA The process of DNA extraction is necessary to isolate molecules of DNA from cells or tissues. A series of steps, including the use of protease enzymes to strip proteins from the DNA, are required for isolating pure DNA that is suitable for use in later procedures, such as cloning or sequencing.

In the context of genetic engineering, reverse transcriptase is an enzyme that catalyzes the synthesis of DNA using messenger RNA (mRNA) as a template. This process is known as reverse transcription.123

The resulting DNA molecules are referred to as complementary DNA (cDNA). Because mRNA molecules carry encoded information from DNA for protein synthesis, using reverse transcriptase allows researchers to create a DNA copy of these transcribed genes.1

This technique is fundamental to the creation of a cDNA library, which provides a sampling of the genes being expressed by an organism. Unlike genomic libraries, which contain the entire genome including untranscribed regions and non-coding introns, cDNA libraries represent only the transcribed sequences. This makes cDNA particularly useful in recombinant DNA technology, as it allows for the expression of eukaryotic proteins in bacterial cells, which otherwise cannot process introns. Additionally, this process is a core component of reverse transcription-polymerase chain reaction (RT-PCR), a powerful laboratory tool used to quantify gene expression.12