Answer:
Mutation.
Step-by-step explanation:
Genetic variation in a population is caused by Mutation , recombination between homologous chromosomes (during meiosis), random fertilization and random mating.
Mutation: Mutation is a change that occur in our nucleotide sequences of the genome of the organism, either due to the results of the environmental factors ( UV lights) or mistakes when the DNA is copied. There are 3 types of DNA mutation present :
1) Deletions
2) Insertions
3) Base Substitutions