Jacobs Syndrome

Jacob’s syndrome 2

Anatomy and Physiology:

Jacob’s syndrome

Over the past 40 years people have been aware of Jacobs’s syndrome, a rare chromosomal genetic syndrome which occurs when a male receives an extra Y chromosome, resulting in a sequence in XYY. Males normally have XY and females normally have XX sequencing 1. Chromosomes store genetic information in all human beings. There are 23 pairs of chromosomes and 46 in total. On the 23rd pair holds the sex chromosomes which also store genetic information that determine ones sex 6. The first reported and documented case of Jacob’s syndrome was researched by Dr. Avery A. Sahaberg in 1961. The syndrome was found in a normal 44-year old man, 6 ft. [183 cm] tall man of average intelligence. Dr. Avery and his colleagues discovered the syndrome at Rosewell Park memorial in Buffalo, New York 4. Roughly ten years after the discovery of the syndrome screenings began in hospitals located in England, Canada, Denmark and US. XYY males and their families were offered anticipatory guidance, but soon after these screenings were put to action they were stopped due to self-fulfilling prophesies 8.

Another name for Jacob’s syndrome is the 47, XYY syndrome. The reason for the name of 47, XYY is “caused by the presence of an extra copy of the Y chromosome in each of a male's cells. As a result of the extra Y chromosome, each cell has a total of 47 chromosomes instead of 46” 7.

The exact cause of Jacob’s Syndrome still stands to be unknown, although there are few presumptions of why this syndrome occurs. The Syndrome results when a male receives two Y chromosomes from the father instead of one, thus the individual receives the sequence of XYY. One cause of Jacob’s syndrome was studied by Robin Julian, who states that Jacob’s syndrome is “not inherited, but usually occurs in a random event during the formation of sperm cells. An error in cell division called nondisjunction can result in sperm cells with an extra copy of the Y chromosome.” An extra Y chromosome in each of the body's cells will develop if one of these reproductive cells contributes to the genetic makeup of the individual. “In some cases, the addition of an extra Y chromosome results from nondisjunction during cell division in early embryonic development. These cases are usually 46,XY/47,XYY mosaics” 7. The ratio of Jacob’s syndrome occurring is approximately 1 in 1001 males, or about 136,000 people in the United States 4.

The symptoms of the unusual chromosome arrangement are the male child may experience learning problems at an early age in school, delayed emotional maturity and behavioral problems. Some examples of learning disabilities at an early age are delayed speech, reading and language skills. There have been some reported cases of aggressive behavior. Individuals with Jacob’s syndrome have been known to have large hands and feet, and an average male who had been previously diagnosed with the syndrome may be taller than average with severe ache breakouts 4, 2. Statistics show that about 96% of Jacob’s syndrome patients are reported to be normal 8. Although these symptoms may occur, there have been no defined findings of any unusual birth defects or any serious future medical problems throughout their life.

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