When an atom gains or loses electrons , the charged particle that results is called a(n)

Ion / Ions

Explanation: When a neutral atoms loses or gains electrons they become charged atoms in which called as ions.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).