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

Verified step by step guidance

1. Understand that nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, which can occur during meiosis I or meiosis II in female gametes.
2. Recognize that Klinefelter syndrome (47,XXY) occurs when a male has an extra X chromosome, which can result from nondisjunction in the female gamete leading to an egg with two X chromosomes (XX). When fertilized by a normal male sperm (Y), the resulting zygote will have XXY.
3. Identify that Turner syndrome (45,X) occurs when a female has only one X chromosome. This can result from nondisjunction in the female gamete leading to an egg with no sex chromosome (O). When fertilized by a normal male sperm (X), the resulting zygote will have a single X chromosome.
4. Consider the stages of meiosis where nondisjunction can occur: in meiosis I, homologous chromosomes fail to separate, and in meiosis II, sister chromatids fail to separate. Both can lead to gametes with abnormal numbers of chromosomes.
5. Reflect on the implications of nondisjunction: it can lead to aneuploidy, a condition where the number of chromosomes is not the typical diploid number, resulting in genetic disorders such as Klinefelter and Turner syndromes.

Key Concepts

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, specifically meiosis. In females, this can lead to gametes with an abnormal number of chromosomes. If such a gamete is involved in fertilization, it can result in offspring with chromosomal disorders, such as Klinefelter syndrome or Turner syndrome.

Klinefelter Syndrome

Klinefelter syndrome is a genetic condition that occurs in males who have an extra X chromosome, resulting in a 47,XXY karyotype. This condition can arise when a normal male gamete fertilizes a female gamete that has undergone nondisjunction, leading to an extra X chromosome. Individuals with Klinefelter syndrome may experience various physical and developmental challenges, including infertility and learning difficulties.

Turner Syndrome

Turner syndrome is a chromosomal disorder that affects females, characterized by the presence of only one X chromosome (45,X karyotype) due to nondisjunction in the female gamete. When a normal male gamete fertilizes a Turner syndrome egg, the resulting offspring will have a missing or incomplete second sex chromosome. This condition can lead to various developmental issues, including short stature and infertility.