Horizontal Gene Transfer

Abstract

Horizontal gene transfer (HGT) may be defined as any occurrence of heritable material passing between organisms, asynchronous with reproduction of the organisms. It represents replication of heritable material outside the context of parent to offspring (i.e. vertical) reproduction. Three types of evidence traditionally lead to claims of HGT. Firstly, biochemical and genetic observations of real-time (usually laboratory recreations of) gene flow between two genotypically distinguishable individuals. Secondly, DNA sequences that are common within a species but inconsistently found in that genus, and finally, direct evidence of processes that can create genes that reproduce horizontally. HGT is now confirmed to occur between all biological kingdoms and has consequences even when genes fail to introgress.