Selfish DNA

Selfish DNA ( also parasitic DNA) describes DNA sequences that do not offer any ostensible benefit to their host and spread in the host genome to another by adding more copies of itself. They are therefore considered to be parasitic. Frequently selfish DNA has no effect on the phenotype of the host. It can occur in the form of mobile genetic elements, but also as a B- chromosome.

Properties

The term was used in 1976 by ​​Richard Dawkins in his book The Selfish Gene for the first time, and learned the following adjustments to the definition. Selfish DNA was originally thought of as a form of non-coding nucleic acids, but has mostly some coding sequences for proteins that serve an increase in translocation and its DNA sequence, eg in inteins, homing endonucleases, insertion sequences, transposons, retroelements or B chromosomes.

Secondary, there is a potentially useful function for the host in the form of an increased ability of the chromosome containing the translocation and an increased genetic adaptability, such as the VDJ recombination. In addition, effects on gene expression were observed by means of a regulation of the transcription of alternative promoters, and by generating a RNA interference. Thus, there is a smooth transition from parasitism to symbiosis in some forms of selfish DNA.