Question

Describe how nondisjunction in human female gametes can give rise to Klinefelter and Turner syndrome offspring following fertilization by a normal male gamete.

Short answer

Answer: Nondisjunction in human female gametes can lead to Klinefelter and Turner syndrome offspring when eggs with abnormal numbers of X chromosomes are fertilized by normal male sperm. If an egg with two X chromosomes is fertilized by sperm carrying a Y chromosome, the offspring will have Klinefelter syndrome (XXY). Alternatively, if an egg lacking an X chromosome is fertilized by sperm carrying an X chromosome, the offspring will have Turner syndrome (XO).

Step-by-step solution

Understand Klinefelter and Turner Syndromes

Klinefelter syndrome is a genetic disorder in males that is caused by the presence of an extra X chromosome (resulting in a genotype of XXY). This condition can lead to a range of physical and developmental symptoms, including infertility, lower levels of testosterone, and an increased risk of certain health problems. Turner syndrome, on the other hand, affects females and arises from the loss of one of the two X chromosomes (resulting in a genotype of XO). Affected individuals typically exhibit a range of physical and developmental anomalies, including short stature, underdeveloped sexual characteristics, and an increased risk of certain health issues. Both Klinefelter and Turner syndromes can result from nondisjunction during the formation of gametes in females. In the following steps, we will describe how this occurs. #Step 2: Understand Nondisjunction#

Understand Nondisjunction

Nondisjunction is a process in which homologous chromosomes or sister chromatids fail to separate properly during cell division. This can lead to the formation of gametes with an abnormal number of chromosomes. It typically occurs during meiosis - the type of cell division responsible for the formation of egg and sperm cells. In human female gametes, nondisjunction can involve the X chromosomes. #Step 3: Nondisjunction and Klinefelter Syndrome#

Nondisjunction and Klinefelter Syndrome

Nondisjunction during meiosis in a human female can lead to the formation of an egg with two X chromosomes instead of the usual one. When this egg is fertilized by a normal male sperm carrying a Y chromosome, the resulting zygote will have three sex chromosomes - two X chromosomes and one Y chromosome (XXY). This is the genetic hallmark of Klinefelter syndrome. Thus, the offspring produced from this fertilization event will have Klinefelter syndrome. #Step 4: Nondisjunction and Turner Syndrome#

Nondisjunction and Turner Syndrome

Nondisjunction can also result in the formation of an egg with no X chromosome at all. When this egg is fertilized by a normal male sperm carrying an X chromosome, the resulting zygote will have only one sex chromosome - an X chromosome, with no corresponding pair (XO). This is the genetic basis of Turner syndrome. The offspring produced from this fertilization event will have Turner syndrome. In summary, nondisjunction in human female gametes can lead to Klinefelter and Turner syndrome offspring following fertilization by normal male gametes. Klinefelter syndrome occurs when an egg with two X chromosomes is fertilized by sperm carrying a Y chromosome, while Turner syndrome results from the fertilization of an egg lacking an X chromosome by sperm carrying an X chromosome.