Answer:
Trisomy
Step-by-step explanation:
A trisomy is a type of polysomy (presence of three or more copies of the chromosome rather than the expected two copies) in which there are three copies of a particular chromosome, instead of the normal two. A trisomy is a also a genetic disorder and a type of aneuploidy (an abnormal number of chromosomes either an increase or a decrease). Examples include trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), trisomy 13 (Patau syndrome)