Principle of Segregation, first established by Mendel, explains the independent separation of the alleles of a gene during gamete formation and their random association with other gametes during fertilisation. This is the reason why sexula reproduction brings about a combination of variabilities in the offsrpings. For example, two round pea plants with the genotype Rr can be crossed to produce a wrinkled pea plant with genotype rr. The two alleles, R and r, do not mix or change each other even though they are present in the same individual. Each allele can contribute to the next generation.