- Overview of Chromosome and Gene Disorders
- Down Syndrome (Trisomy 21)
- Trisomy 18
- Trisomy 13
- Overview of Chromosomal Deletion Syndromes
- Cri-du-Chat Syndrome
- Prader-Willi Syndrome
- Wolf-Hirschhorn Syndrome
- Overview of Sex Chromosome Abnormalities
- Fragile X Syndrome
- Klinefelter Syndrome
- Noonan Syndrome
- Trisomy X
- Turner Syndrome
- XYY Syndrome
XYY syndrome is a sex chromosome abnormality in which boys are born with 2 Y chromosomes and 1 X chromosome.
Chromosomes are structures within cells that contain DNA and many genes. Genes contain instructions that determine how the body is supposed to look and function.
The sex chromosomes determine whether a fetus becomes male or female. A pair of X and Y chromosomes (XY) results in a male, and a pair of X and X chromosomes (XX) results in a female.
About 1 in every 1,000 boys is born with XYY syndrome.
Boys with XYY syndrome tend to be tall and have difficulties with language. Their intelligence quotient (IQ) tends to be slightly lower than that of other family members. There are few physical abnormalities. Minor learning disabilities, attention-deficit/hyperactivity disorder, and other behavioral disorders can develop.
XYY syndrome was once thought to cause aggressive or violent criminal behavior, but this theory has been disproved.
