Genetic drift is also known as the Sewall Wright effect and genetic sampling error. It is a change in the gene pool of a small population which takes place strictly by chance. This leads to genetic traits being lost from a population or becoming widespread in a population without respect to the survival or reproductive value of the alleles involved. Genetic drift over the generations can result in the complete loss of one allele in an allele pair. The chance of occurring genetic drift is more in small, isolated populations in which the gene pool is small enough.