Klinefelter’s Syndrome - Tara Ashford

How? Extra X Chromosome(XXY)/ 47(XXY) Nondisjunction in Meiosis 1 Nondisjunction occurs when homologous chromosomes, in this case the X and Y sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome. Fertilizing a normal (X) egg produces an XXY offspring -Most common genetic variation that occurs in 1 out of 500 live male births -Another mechanism for retaining the extra X chromosome is through a nondisjunction event during Meiosis 2 in the female. Nondisjunction will occur when sister chromatids on the sex chromosome, in this case an X and an X, fail to separate. An XX egg is produced which, when fertilized with a Y sperm, yields XXY offspring.

Continued -Some males with Klinefelter syndrome have the extra X chromosome in only some of their cells; in these individuals, the condition is described as mosaic Klinefelter syndrome (46,XY/47,XXY). Individuals with mosaic Klinefelter syndrome may have milder signs and symptoms depending on how many cells have an additional X chromosome Gene Mutation

History -In 1942, Dr. Harry Klinefelter and his coworkers at the Massachusetts General Hospital in Boston published a report about 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm -Late 1950’s researches discovered that it was Klinefelter’s Syndrome

Hereditary Not Hereditary (Random) Advanced maternal age increases the risk for the XXY chromosome Recent Klinefelter syndrome research shows that half the time, the extra chromosome comes from the father.

Phenotypic Effects Child -Weaker Muscles -Reduced Strength -Less Muscle Control Teen -Not as much Testosterone -Less Facial/Body Hair -Broader Hips -Larger Breasts -Weaker Bones -Lower Energy Level Adult -Tall -Infertile

Cognitive and developmental Some degree of language learning or reading impairment may be present May also be delays in motor development which can be addressed through occupational therapy May sit up, crawl, and walk later than other infants; they may also struggle in school, both academically and with sports.[4]

Diagnosis -Determination of the sex chromatin -Prenatally, Chorionic Villus Sampling or Amniocentesis - 58% of pregnancies in the United States with a diagnosis of Klinefelter syndrome were terminated -About 10% of Klinefelter cases are found by Prenatal Diagnosis Only a quarter of the affected males are recognized as having Klinefelter syndrome at puberty 25% are diagnosed in late Adulthood Standard diagnostic method is the analysis of the chromosomes' Karyotype on Lymphocytes - Dermal fibroblasts or testicular tissue

Treatment Genetic Variation irreversable Testosterone treatment should began at puberty This treatment can normalize body proportions and promote development of normal secondary sex characteristics but does not treat infertility

Random Facts -Reduces life expectancy 3.1 % of infertile males have Klinefelter syndrome The syndrome is also the main cause of male hypogonadism Prevalence of the syndrome has increased over the past decades

Bibliography http://www.genetics.edu.au/Information/Genetics-Fact-Sheets/KlinefelterSyndromeXXYSyndromeFS31/at_download/file -http://en.wikipedia.org/wiki/Klinefelter_syndrome -http://genetics.emedtv.com/klinefelter-syndrome/is-klinefelter-syndrome-hereditary.html -http://ghr.nlm.nih.gov/condition/klinefelter-syndrome