What Causes XYY Syndrome?

XYY syndrome is a rare genetic disorder that affects only males. The symptoms of this chromosomal birth defect are very few. Most men with XYY syndrome live a normal life with normal sexual development and fertility. Some men with this condition develop certain signs and symptoms which include:

• Learning disability
• Speech problems
• Delayed motor skill development
• Taller than average height
• Behavioral problems
• Lower IQ
• Weaker muscle

With early diagnosis and proper treatment, men with this condition can live a normal successful life.

Causes of XYY syndrome

Let's discuss below what causes XYY syndrome.

A normal human being has 46 chromosomes in each cell which are divided into 23 pairs. These 46 chromosomes include one X and one Y chromosomes, also known as the sex chromosomes. The sex chromosomes determine the female and male sex characteristics. Women have two X chromosomes whereas are men have one X and one Y chromosome. However, men born with XYY syndrome have one X and two Y chromosomes.

XYY syndrome is not hereditary. Chances of having children with XYY syndrome are more or less the same for men without XYY syndrome as it for those with XYY syndrome. This condition is caused due to the error in cell division. The improper segregation of chromosomes or nondisjunction during anaphase II of sperm formation can result in an extra copy of the Y chromosome. This cell-division error can happen prior to conception in either the mother’s or father's reproductive cells.

In some rare cases, the XYY syndrome can occur due to the nondisjunction after conception. This happens in the early embryonic development stages. Such male infants may be born with a mosaic of cells of which some have 46 chromosomes and other 47 chromosomes. The exact cause behind this nondisjunction, both before and after conception is still not known.