The 47,XXY karyotype of Klinefelter syndrome spontaneously arises when paired X chromosomes fail to separate (nondisjunction in stage I or II of meiosis, during oogenesis or spermatogenesis). Maternal and paternal meiotic nondisjunction each account for approximately 50% of Klinefelter syndrome cases.
How does nondisjunction result in Klinefelter syndrome?
However, because of nondisjunction, an egg cell or a sperm cell can also end up with an extra copy of the X chromosome. If an egg cell with an extra X chromosome (XX) is fertilized by a sperm cell with one Y chromosome, the resulting child will have Klinefelter syndrome.
Does Klinefelter’s occur in meiosis 1 or 2?
The most frequent chromosomal complement associated with Klinefelter syndrome is 47,XXY, which may result from a nondisjunction during (1) meiosis I or meiosis II of oogenesis, or (2) meiosis I of spermatogenesis.
What is nondisjunction in Klinefelter syndrome?
Klinefelter syndrome usually occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes .
What stage of meiosis causes Klinefelter syndrome?
Klinefelter’s syndrome, XXY males, can occur due to nondisjunction of X chromosomes during prophase of meiosis I in females. One of the eggs from such a meiosis could receive both X chromosomes, and the other would receive no X chromosomes.
What happens during nondisjunction in meiosis?
Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in an abnormal chromosome number.
Which meiosis does Klinefelter syndrome occur?
What happens in Klinefelter syndrome?
Klinefelter syndrome may adversely affect testicular growth, resulting in smaller than normal testicles, which can lead to lower production of testosterone. The syndrome may also cause reduced muscle mass, reduced body and facial hair, and enlarged breast tissue.
What is Klinefelter syndrome in meiosis?
A boy born with Klinefelter syndrome has an extra X chromosome that is believed to be caused by a random error. This error usually occurs during meiosis when the cell divides to produce the sperm or the egg cell in the father or mother, respectively.
Does Klinefelter syndrome happen in meiosis 1?
What mutation causes Klinefelter syndrome?
Males have an X and a Y sex chromosome (XY). Klinefelter syndrome can be caused by: One extra copy of the X chromosome in each cell (XXY), the most common cause. An extra X chromosome in some of the cells (mosaic Klinefelter syndrome), with fewer symptoms.
What is the role of nondisjunction in Klinefelter syndrome?
Role of Nondisjunction. Therefore, nondisjunction accounts for the presence of a trisomy of sex chromosomes. The trisomy pattern of Klinefelter’s can occur through various errors. A maternally derived XXY pattern can be traced to an error that occurs during meiosis I, meiosis II, or early mitotic division stages.
How does Klinefelter syndrome occur?
Most commonly, Klinefelter syndrome occurs due to a process referred to as nondisjunction in the egg or the sperm during meiosis. Meiosis is the process by which genetic material is multiplied and then divided to supply a copy of genetic material to an egg or a sperm. In a nondisjunction, the genetic material is improperly separated.
Can there be more than one X chromosome in Klinefelter syndrome?
In some cases, there is more than one X chromosome in each cell (for example, 48,XXXY or 49,XXXXY). These conditions, which are often called “variants of Klinefelter” syndrome usually have more serious problems ( intellectual disability, skeletal problems, and poor coordination) than classic Klinefelter syndrome (47,XXY). [3]
Is Mosaic Klinefelter syndrome inherited?
Mosaic Klinefelter syndrome (46,XY/47,XXY) is also not inherited. It occurs as a random error during cell division early in fetal development. As a result, some of the body’s cells have the usual one X chromosome and one Y chromosome (46,XY), and other cells have an extra copy of the X chromosome (47,XXY).
