: Polyploidy is a condition in which the chromosome number is two or more times the normal haploid number found in gametes. It may occur in nature or can be induced artificially by using colchicines. This type of mutation includes all the cases in which any change in number of chromosomes in set wise occurs. Entry of more than one sperm nucleus into an ovum at fertilization is called polyspermy. Fusion of a male gamete with secondary nucleus is termed as double fertilization.