käänteiskopiointireaktio

Käänteiskopiointireaktio, also known as reverse transcription, is a biological process where an RNA molecule is used as a template to synthesize a complementary DNA (cDNA) molecule. This process is the reverse of the usual flow of genetic information, which goes from DNA to RNA through transcription. The enzyme responsible for catalyzing this reaction is called reverse transcriptase.

Reverse transcriptase is primarily found in retroviruses, such as HIV. When a retrovirus infects a host cell, it injects its RNA genome into the cytoplasm. The reverse transcriptase enzyme then converts this viral RNA into a double-stranded DNA molecule. This viral DNA is then integrated into the host cell's genome, where it can be transcribed and translated to produce new viral particles.

In addition to retroviruses, reverse transcriptase activity is also found in eukaryotic cells. Mobile genetic elements called retrotransposons utilize reverse transcription to move around the genome. Furthermore, reverse transcriptase plays a crucial role in maintaining the ends of eukaryotic chromosomes, known as telomeres, with the help of an enzyme called telomerase, which contains an RNA template.

The discovery of reverse transcriptase by Howard Temin and David Baltimore in 1970 was a significant breakthrough in molecular biology. It provided strong evidence for the existence of the RNA-to-DNA information transfer and opened up new avenues for research, including the development of diagnostic tools and antiviral therapies. The ability to synthesize cDNA from RNA is also a fundamental technique in molecular biology laboratories, used in applications like complementary DNA libraries and quantitative polymerase chain reaction (qPCR).