käänteistranskriptiona

Käänteistranskriptiona, sometimes referred to as reverse transcription, is a process where RNA is used as a template to synthesize a complementary DNA (cDNA) molecule. This biological process is primarily carried out by a group of enzymes called reverse transcriptases. These enzymes are found in retroviruses, such as HIV, and also in eukaryotes.

In retroviruses, reverse transcriptase is essential for their replication cycle. When a retrovirus infects a host cell, it injects its RNA genome and the reverse transcriptase enzyme. The reverse transcriptase then uses the viral RNA as a template to create a DNA copy, which is subsequently integrated into the host cell's genome. This integrated viral DNA can then be transcribed and translated to produce new viral particles.

In eukaryotes, reverse transcriptase activity is associated with mobile genetic elements called retrotransposons and with telomerase. Retrotransposons are DNA sequences that can move within the genome, and their movement often involves an RNA intermediate and reverse transcription. Telomerase is a specialized reverse transcriptase that maintains the ends of chromosomes, known as telomeres, preventing them from shortening with each round of DNA replication.

The discovery of reverse transcriptase by Howard Temin and David Baltimore in the late 1960s and early 1970s was a significant breakthrough in molecular biology. It challenged the central dogma of molecular biology, which at the time stated that genetic information flows only from DNA to RNA. Reverse transcriptase demonstrated that the flow of genetic information could also occur in the reverse direction, from RNA to DNA. This discovery has had profound implications for our understanding of viral replication, gene expression, and genome evolution, and it has led to the development of important molecular tools used in research and biotechnology, such as the polymerase chain reaction (PCR) and gene cloning.