Selfish DNA is a term used to describe sequences of DNA that replicate and spread within a genome with little or no benefit to the organism carrying them. The word 'selfish' is pronounced as /ˈsɛlfɪʃ/ with the stress on the first syllable. The 's' is pronounced as the voiceless alveolar fricative sound /s/ followed by the short vowel sound /ɛ/. The word 'DNA' is pronounced as /diː.ɛn.eɪ/ with the stress on the first and third syllables. It is written in all capital letters to distinguish it from the word 'dna' which means deoxyribonucleic acid.
Selfish DNA refers to a theoretical concept in the field of genetics that describes genetic elements or sequences that propagate themselves in a host genome, often at the expense of their host's fitness or reproductive success. These genetic elements, also known as mobile genetic elements or transposable elements, are DNA sequences that have the ability to move or duplicate themselves within a genome. They are considered "selfish" because they often do not confer any direct benefits to the hosts in which they reside.
Selfish DNA can be classified into various types, such as transposons and retrotransposons, based on their mechanism of movement within a genome. Transposons move directly from one chromosomal site to another, while retrotransposons are first transcribed into RNA and then inserted back into the genome through a reverse transcription process. These mobile genetic elements can proliferate through processes such as DNA replication, recombination, and transposition.
While selfish DNA is generally considered parasitic and detrimental to the host, some evolutionary biologists argue that it can have positive effects on the evolution of genomes. For instance, selfish DNA elements may contribute to genetic diversity, promote genomic rearrangement, or drive the evolution of reproductive isolation between populations. However, the overall impact of selfish DNA elements on both the host organisms and their genomes is still a topic of active research and debate in evolutionary biology.
The term "Selfish DNA" was coined by Richard Dawkins in his book "The Selfish Gene" published in 1976. The etymology of the term originates from Dawkins' concept of genetic material (DNA) acting selfishly in the process of evolution.