Which of the following does not allow genetic variation to occur

a) genetic mutation
b) gene shuffling
c) crossing-over
d) mitosis

Ans. Option D). mitosis.

Genetic variations may defined as variations between individuals of same or different species due to variant genes. Genetic variations may arise due to process of mutation, crossing over, gene shuffling, and random mating as these processes provide cells or organisms with new combinations.

Mitosis occurs in somatic cells or normal body cells and provides cells, having exact genetic makeup as present in parent organism. Hence, it cannot affect the genetic composition of organisms that may cause genetic variation.

Thus, the correct answer is option D). 'mitosis.'