Which process most contributes to genetic variation in a population?

Recombination of homologous chromosomes in meiosis most contributes to genetic variation in a population.

Explanation:

Genetic variation is a process in which DNA sequences change in the genome of individuals causing to have new traits. The new alleles entered the population will cause variation.

genetic variation is caused by following processes:

mutation, meiosis, random mating and gene flow.

In the fertilization of each parent contributes its one gamete either egg or sperm as haploid cells. These fuse to form zygote. In the process of meiosis during recombination of homologous chromosomes variation is made. Also meiosis has pattern of independent assortment because each cell has its own DNA. Thus meiosis creates a great genetic variation in population. It is because of meiosis that no two siblings or individual in a population looks exactly same except identical twins.

Mutation: It can happen at any time in replication and can cause change in alleles or genes and result in new traits.

Random mating: When individuals choose to mate with an individual having traits that are similar or superior to them.

gene flow : It is the migration of alleles from different population. This also creates genetic variation.