Final answer:
Gene conversion involves the nonreciprocal transfer of genetic information from one DNA helix to another during the resolution of a Holliday junction, leading to alterations in one helix without reciprocal changes.
Step-by-step explanation:
In gene conversion, the nonreciprocal resolution of a Holliday junction results in the transfer of genetic information from one DNA helix to another without a reciprocal exchange. This process leads to one of the DNA helices being altered to match the sequence of the other. During the normal process of homologous recombination, when a crossover event occurs through the formation of a Holliday junction, equal amounts of genetic information are typically exchanged between two non-sister chromatids, creating a reciprocal exchange of equivalent DNA. However, gene conversion is a deviation from this reciprocal nature.
During the resolution of the Holliday junction, which is a cross-shaped structure formed between two double-stranded DNA molecules, the enzymes involved may decide to follow a path that ‘copies’ the genetic information of one strand onto the other, rather than exchanging analogous segments. Consequently, the genetic sequence of one chromosome is converted to that of the other, without the other chromosome reciprocally altering its sequence. This phenomenon can result in important genetic variations and has implications in the evolution of genomes and the repair of DNA damages.