Host organisms respond with a battery of strategies to mitigate the harmful effects of TE invasion. A good example is a clever strategy adopted by some yeast transposons which jump into the host chromosome on top of each other, piggybacking for a common point of entry into the genome. Not only do these TE invaders not wreak damage in their host's body cells, but by targeting germ cells they ensure their own survival in the host's progeny. A good example of this strategy is the P element Kidwell has long studied in fruit flies. This element only jumps in germline cells.
Harmful mutations cause dysfunction and disease in host organisms.
A type of muscular dystrophy in humans is one example. But in terms of populations and species, deleterious mutations are usually eliminated by natural selection, Kidwell said. Or mutations can be benign or neutral, as in the case of speckled and striped varieties of the Japanese morning glory, for example. New studies also show that mutations in the long term can be positive and contribute to the evolution and survival of species. A fundamental part of the vertebrate immune system apparently resulted from a transposable element called RAG that played a critical role early in vertebrate evolution, Kidwell said.