Jacob syndrome or also known as XYY syndrome is found in about 1 in 1000 boys. Most people have 46 chromosomes in each cell. In men, this usually includes one X chromosome and one Y chromosome (XY).

Jacobs syndrome is not genetic, though the exact reasons for the chromosomal misfire are unclear. It appears to be somewhat random, resulting from flaws in the cell division process of the Y ...

The syndrome is commonly known as Jacob’s syndrome, Superman syndrome, XYY karyotype, XYY syndrome, YY syndrome, and 46,XY/47,XYY mosaicism.

Men with an extra X chromosome, known as Klinefelter syndrome, or Y chromosome, also known as Jacobs syndrome, have an increased risk of delayed development, learning disabilities, type 2 diabetes ...

The skeleton with an extra Y chromosome also showed osteological evidence consistent with Jacobs syndrome (male, 46+ years, dated 680 to 890 CE); ...

Men with an extra X chromosome, known as Klinefelter syndrome, or Y chromosome, also known as Jacobs syndrome, have an increased risk of delayed development, learning disabilities, type 2 diabetes ...