XYY Karyotype

Definition

XYY syndrome is a chromosome disorder that affects males. Males with this disorder have an extra Y chromosome.

Description

The XYY syndrome was previously considered the super-male syndrome, in which men with this condition were thought to be overly aggressive and more likely to become criminals. These original stereotypes came about because several researchers in the 1960s found a high number of men with XYY syndrome in prisons and mental institutes.

These original observations did not consider that the majority of males with XYY syndrome were not in prisons or mental institutes. Since then, broader, less biased studies have been done on males with XYY syndrome. Though males with XYY syndrome may be taller than average and have an increased risk for learning difficulties, especially in reading and speech, they are not overly aggressive. Unfortunately, some text books and many people still believe the inaccurate stereotype of the super-male syndrome.

Genetic profile

Chromosomes are structures in the cells that contain genes. Genes are responsible for instructing our bodies how to grow and develop. Usually, an individual has 46 chromosomes in each cell, or 23 pairs. The first 22 pairs are the same in males and females and the last pair, the sex chromosomes, consist of two X chromosomes in a female, and an X chromosome and an Y chromosome in a male.

XYY syndrome occurs when an extra Y chromosome is present in the cells of an affected individual. People with XYY syndrome are always male. The error that causes the extra Y chromosome can occur in the fertilizing sperm or in the developing embryo.

XYY is not considered an inherited condition. An inherited condition usually is one in which the mother and/or father has an alteration in a gene or chromosome that can be passed onto their children. Typically, in an inherited condition, there is an increased chance that the condition will reoccur. The risk of the condition reoccurring in another pregnancy is not increased above the general population incidence.

Demographics

XYY syndrome has an incidence of one in 1,000 newborn males. However, since many males with XYY syndrome look like other males without XYY syndrome, many males are never identified.

Content licensed from:

Author Info: Carin Lea Beltz MS, CGC, Thomson Gale, Gale, Detroit, Gale Encyclopedia of Genetic Disorders Part II, 2005

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.