The sex chromosomes and Trisomy 21(Down Syndrome) are generally the only survivable full chromosome aneuploidies and all include varying degrees of deficit. There are several aneuploid conditions that are created by partial chromosome losses that also result in varying degrees of

deficit.

Aneuploid - the individual has an extra copy of one chromosome or is missing a chromosome.

The failure of chromosomes to separate during mitosis results in one gamete that lacks a chromosome and another with 2 chromosomes. Gametes with improper number of chromosomes are called aneuploid gametes. Aneuploid gametes are the most common cause of spontaneous abortion and handfuls of other congenital disorders that varies depending on donors gamete content.

An example of aneuploid condition is Down syndrome, is due to three copies of choromosome 21 or trisomy 21.