A<unk>  is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A<unk>  is a type of aneuploidy (an abnormal number of chromosomes).
Trisomy
Robertsonian translocation
Anticipation 
Caudal duplication
Polyploidy
Agenesis
Germline mosaicism
Heteroxeny