Final answer:
The selfish DNA theory describes the proliferation of transposable elements in a genome, likening their behavior to that of a parasite. It was once thought that transposons only served to replicate themselves, but research has shown they play critical roles in increasing genetic diversity and potentially providing evolutionary benefits.
Step-by-step explanation:
The selfish DNA theory attempts to explain the proliferation of transposable elements in a genome. The theory compares the action of these elements to that of a parasite. It was proposed that much of the non-coding DNA in eukaryotic genomes, which includes transposons, seems to serve no other purpose than its own replication.
Transposons or transposable elements, also known as 'jumping genes', were once thought to be junk DNA, but are now understood to play a role in increasing genetic diversity, potentially providing an evolutionary advantage to the host organism.
Transposons are found throughout eukaryotic genomes and have been discovered in all types of organisms, indicating an early evolutionary origin. Their ability to move within the genome, sometimes referred to as transposition, can result in mutations, which can lead to the adaptation of the organism.
Transposons contribute to genetic diversity, and in the long term, their presence within genomes might have been selected for due to the benefits they provide in terms of genetic regulation and evolutionary potential.
The original misunderstanding of transposons as junk DNA highlights the complexity of genome evolution and the ongoing research in understanding the intricacies of genetic elements and their effects on an organism's physiology and survival.