When a change in the chromosome number does not involve entire sets of chromosome and restrict to only a few of chromosome, the situation is called aneuploidy. Aneuploidy may be of following types [a] Monosomic (2n−1) [b] Trisomic (2n+1) [c] Nullisomic (2n−2) [d] Terrasomic (2n+2) [e] Double monosomic (2n−1−1) [f] Double trisomic (2n+1+1)