C+&+GD--+Abnormal+Numbers+of+Sex+Chromosomes

= //C & GD-- Abnormal Numbers of Sex Chromosomes // =

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Nondisjunction is the cause abnormal numbers of sex chromosomes. Unusual numbers of sex chromosomes seem to upset the genetic balance. A chromosome abnormality that causes individuals to have an abnormal number of chromosomes is called aneuploidy. If the zygote has an additional chromosome it is trisomic for that chromosome. If the zygote is missing a chromosome it is monosomic. In sex chromosomes, nondisjunction results in a number of abnormalities, such as Klinefelter syndrome, Normal male, Metafemale, and Turner syndrome. =====

**__Klinefelter's Syndrome; XXY Syndrome __**
Klinefelter's syndrome is a condition in which human males have an extra X chromosome. The sex chromosomes of this condition are XXY. In humans, Klinefelter's syndrome is the most common sex chromosome disorder. The origin of nondisfunction is meiosis in egg or sperm formation. The fequency in population is 1 out of every 2000. The principal effects are development of small testicles and reduced fertility. A variety of other physical and behavioral differences and problems are common, though severity varies and many boys and men with the condition have few detectable symptoms.

__Normal Male; XYY Syndrome﻿ __
Human males with a single extra Y chromosome (XYY) do not have any well-defined syndrome, although they tend to be taller than average. Usually, the extra Y chromosome won't cause any unusual physical features or medical problems. The origin of nondisjunction is meiosis in sperm formation. The frequency in population in 1 in every 2000.



__Metafemale; XXX Syndrome __
A metafemale is a term given to female with one additional female chromosome.The proper term for this abnormality is 'Triple X syndrome' which is basically a form of chromosomal variation. It is characterized by an extra X chromosome which is present in each and every cell of a female. This condition results at the time of division of any parent's reproductive cells. The origin of this nondisjunction is meiosis in egg or sperm formation. The frequency in population is 1 in every 1000 females. They have limited fertility but are otherwise apparently normal. 

__Turner Syndrome; XO Syndrome __
 ﻿Turner Syndrome is a disorder that is caused by the absense of a sex chromosome. Most girls are born with two X chromosomes, but girls with Turner syndrome are born with only one X chromosome or they are missing part of one X chromosome. The effects of the condition vary widely among girls with Turner syndrome. It all depends on how many of the body's cells are affected by the changes to the X chromosome. Girls with Turner syndrome are usually short in height. Girls with Turner syndrome who aren't treated for short stature reach an average height of about 4 feet 7 inches. The good news is that when Turner syndrome is diagnosed while a girl is still growing, she can be treated with growth hormones to help her grow taller. In addition to growth problems, Turner syndrome prevents the ovaries from developing properly, which affects a girl's sexual development and the ability to have children. The origin of nondisjunction is meiosis in egg and sperm formation. The frequency in population is 1 in every 5000 famales.  