THE MOLECULAR BASIS OF INHERITANCE
THE HUMAN GENOME
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Detailed explanation-1: -In 1959, Klinefelter syndrome was found to be caused by a supernumerary X chromosome in a male. 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).
Detailed explanation-2: -Down syndrome is caused by a random error in cell division that results in the presence of an extra copy of chromosome 21. The type of error is called nondisjunction (pronounced non-dis-JUHNGK-shuhn).
Detailed explanation-3: -Turner syndrome occurs when part or all of an X chromosome is missing from most or all of the cells in a girl’s body. A girl normally receives one X chromosome from each parent. The error that leads to the missing chromosome appears to happen during the formation of the egg or sperm.