Recombination

Recombination is a process that involves crossing over between chromosomes which subsequently results in exchange of genetic material between the chromosomes. There are three types of genetic recombination and they are homologous recombination, site-specific recombination and somatic recombination. The process normally involves strand invasion followed by strand breakage, which leads to formation of Holliday junction. Resolution of Holliday junction gives rise crossover or noncrossover products. Mismatch repair of heteroduplexes which usually occurs after that may lead to gene conversion. 

Homologous recombination, independent assortment of chromosomes during meiosis and random fertilisation of parental gametes are the main contributors of genetic variation in offspring.