Retrotransposition

Retrotransposition is a biological process that involves the copying of RNA molecules and their insertion into new locations within the genome. This process is facilitated by retrotransposons, which are genetic elements that can amplify themselves in a genome. Retrotransposition is a significant source of genetic variation and plays a crucial role in the evolution of species.

Mechanism of Retrotransposition

Retrotransposition begins with the transcription of a retrotransposon from DNA to RNA. This RNA molecule then serves as a template for the synthesis of complementary DNA (cDNA) through a process known as reverse transcription. The newly synthesized cDNA is then integrated back into the genome at a new location. This process is facilitated by an enzyme called integrase, which is encoded by the retrotransposon itself.

Types of Retrotransposons

There are two main types of retrotransposons: Long Interspersed Nuclear Elements (LINEs) and Short Interspersed Nuclear Elements (SINEs). LINEs are typically 6,000-8,000 base pairs long and encode two proteins necessary for their retrotransposition. SINEs, on the other hand, are shorter (approximately 100-400 base pairs) and do not encode any proteins. Instead, they hijack the proteins encoded by LINEs to facilitate their own retrotransposition.

Role in Genetic Variation and Evolution

Retrotransposition is a major source of genetic variation. By inserting themselves into new locations in the genome, retrotransposons can disrupt genes, alter gene expression, and create new genes. This can lead to the evolution of new traits and adaptations. In fact, it is estimated that up to two-thirds of the human genome has been shaped by retrotransposition.

Retrotransposition and Disease

While retrotransposition can drive evolution and genetic diversity, it can also lead to disease. For example, when retrotransposons insert themselves into genes, they can disrupt the normal function of those genes and lead to genetic disorders. Some cancers have also been linked to the activity of retrotransposons.

See Also

• Transposon
• Genetic Variation
• Evolution
• Genetic Disorders