A familial extra small marker autosome in persons with normal phenotype.

The propositus was referred because of sterility and oligospermia. His karyotype was 45, XY, t(13q14q). His father was dead; his mother and the only brother, who was fertile, both had 47 chromosomes, but a normal phenotype and normal intelligence. The additional chromosome was three quarters the size of a G chromosome and had satellites on the short and long arms.