Is a trisomic organism best described as an aneuploid or a polyploid? Briefly explain. Solution A trisomic organism is the result of aneuploidism. Aneuploid organisms differ in the chromosome number with wild type by one or two chromosomes. For example if 2n is the normal genotype of wild strain, then in trisomic organism, the genotype would be 2n+1. Non dysjunction during mitosis or meiosis is the most common cause of aneuploid organisms. If it is 2n-1,it is nullisomic..