What is XYY Syndrome


Wikipedia XYY Syndrome

Unique– Understanding Chromosome Disorders


XYY Syndrome is a genetic condition that occurs when a male’s genes have an extra Y chromosome. Females typically have two X chromosomes (XX). Males typically have one X chromosome and one Y chromosome (XY). Males with this genetic condition have an extra copy of the Y chromosome in each of their cells (XYY).

Most people have 46 chromosomes in each cell. Males with XYY syndrome have 47 because of the extra copy of the Y chromosome. However, sometimes this mutation is only present in some cells. According to the National Institutes of Health, XYY syndrome occurs in 1 out of every 1,000 boys (Genetics Home Reference).

XYY Syndrome is also sometimes called Jacob’s Syndrome, XYY Karyotype, or YY Syndrome.

Males with XYY Syndrome live typical lives for the most part. Some males with XYY Syndrome may be taller than average and face learning difficulties or speech problems. They may also grow up with minor physical differences, such as weaker muscles and bones and delayed puberty. When they are older, men with the syndrome may face fertility issues and complications related to low testosterone levels. Besides these complications, however, males with XYY syndrome do not usually have any distinguishing physical features or complications, and have normal sexual development.

Source: http://www.healthline.com/health/xyy-syndrome#Overview1

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XYY Syndrome


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  1. I was told by specialists that the “common ” for all sufferers are
    Zero sperm count.
    Giant size ( over 6 foot 4 inches)
    and usually small hands.
    Most other difficulties are a mixed bag, which some have and some don’t.

  2. We were told our son had klinefelter syndrome at the age of 2yr through a blood test our doctor did.

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