Genetic draft, also called hitchhiking, has two components, background selection and selective sweep (Charlesworth & Guttman 1996; Hey 1999; Otto 2000). In background selection, neutral mutations are removed from the gene pool of the population, because they are located on a chromosome in the vicinity of newly formed selectively negative mutations and are eliminated together with them. In selective sweep, on the other hand, neutral polymorphism disappears because, from time to time, an allele containing a positive mutation is fixed in the population. In both cases, only mutations located sufficiently close to the relevant (negatively or positively) allele are affected. This means that, in sections of the genome with limited crossing-over frequency, both processes are especially effective and can even completely eliminate all polymorphism. This phenomenon can be responsible for low polymorphism in the unrecombined parts of the sex heterochromosome (Kreitman 1996) and, to a considerable degree, also for species cohesion in organisms without sexual reproduction (see XX.188.8.131.52).
The terminology related to genetic draft is not yet firmly established. A number of authors use the term evolutionary hitchhiking (draft) basically as a synonym for the term selective sweep, while background selection is not included in the category of evolutionary hitchhiking (Aquadro, Begun, & Kindahl 1994).
a process that is also called the hitchhiking effect or genetic hitchhiking