chromosomal anomaly(n = noun.state) chromosomal aberration, chromosonal disorder, chrosomal abnormality - any change in the normal structure or number of chromosomes; often results in physical or mental abnormalities;
is a kind of aberrance, aberrancy, aberration, deviance
has particulars: monosomy, trisomy, sex-linked disorder

anomaly, chromosomal, chromosomal aberration, chromosomal mutation, congenital anomaly, true anomaly