Overview of chromosomal anomalies

[Gregory]

Chromosomal anomalies cause various disorders. Anomalies that affect autosomes (the 22 paired chromosomes that are alike in males and females) are more common than those that affect sex chromosomes (X and Y).
Chromosomal abnormalities fit into several categories but broadly may be considered as numerical or structural.
Numerical abnormalities include

Trisomy (an extra chromosome)
Monosomy (a missing chromosome)

Structural abnormalities include

Translocations (anomalies in which a whole chromosome or segments of chromosomes inappropriately join with other chromosomes)
Deletions and duplications of various parts of chromosomes