Selective sweep

[5] Because selective sweeps allow for rapid adaptation, they have been cited as a key factor in the ability of pathogenic bacteria and viruses to attack their hosts and survive the medicines we use to treat them.

[6] In such systems, the competition between host and parasite is often characterized as an evolutionary "arms race", so the more rapidly one organism can change its method of attack or defense, the better.

A similar case can be found in Toxoplasma gondii, a remarkably potent protozoan parasite capable of infecting warm-blooded animals.

It appears then, that a novel genotype emerged containing this form of Chr1a and swept the entire European and North American population of Toxoplasma gondii, bringing with it the rest of its genome via genetic hitchhiking.

Cultivated crops, for example, have essentially been genetically modified for more than ten thousand years,[9] subjected to artificial selective pressures, and forced to adapt rapidly to new environments.

In a sense, the long-buried sweeps may give evidence of corn's, and teosinte's, ancestral state by elucidating a common genetic background between the two.

A Swedish research group recently used parallel sequencing techniques to examine eight cultivated varieties of chicken and their closest wild ancestor with the goal of uncovering genetic similarities resultant from selective sweeps.

[11] They managed to uncover evidence of several selective sweeps, most notably in the gene responsible for thyroid-stimulating hormone receptor (TSHR), which regulates the metabolic and photoperiod-related elements of reproduction.

This is a diagram of a hard selective sweep. It shows the different steps (a beneficial mutation occurs, increases in frequency and fixes in a population) and the effect on nearby genetic variation.
This is a diagram of a soft selective sweep from standing genetic variation. It shows the different steps (a neutral mutation becomes beneficial, increases in frequency and fixes in a population) and the effect on nearby genetic variation.
This is a diagram of a multiple origin soft selective sweep from recurrent mutation. It shows the different steps (a beneficial mutation occurs and increases in frequency, but before it fixes the same mutation occur again on a second genomic background, together, the mutations fix in the population) and the effect on nearby genetic variation.