Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

6. Chromosomal Variation

Chromosomal Mutations: Aneuploidy

Genetics

6. Chromosomal Variation

Chromosomal Mutations: Aneuploidy

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2:22 minutes

Problem 9

Textbook Question

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

Understand the concept of nondisjunction: Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis. This can occur during meiosis I (failure of homologous chromosomes to separate) or meiosis II (failure of sister chromatids to separate).

Explain how nondisjunction in female gametes can lead to Klinefelter syndrome: If nondisjunction occurs in the X chromosomes during oogenesis, the resulting egg may contain two X chromosomes (XX). When this egg is fertilized by a normal male sperm carrying a Y chromosome, the resulting zygote will have the karyotype 47,XXY, which is characteristic of Klinefelter syndrome.

Explain how nondisjunction in female gametes can lead to Turner syndrome: If nondisjunction occurs in the X chromosomes during oogenesis, the resulting egg may lack an X chromosome (denoted as 0, or nullisomic for the X chromosome). When this egg is fertilized by a normal male sperm carrying an X chromosome, the resulting zygote will have the karyotype 45,X, which is characteristic of Turner syndrome.

Highlight the role of the normal male gamete: In both cases, the male gamete contributes either an X or a Y chromosome, which combines with the abnormal female gamete to determine the final karyotype of the offspring.

Summarize the outcomes: Nondisjunction in female gametes can result in aneuploidy (abnormal chromosome number) in the offspring. Fertilization of an XX egg with a Y sperm leads to Klinefelter syndrome (47,XXY), while fertilization of a 0 egg with an X sperm leads to Turner syndrome (45,X).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, specifically meiosis. This error can lead to gametes with an abnormal number of chromosomes. In females, if nondisjunction occurs during the formation of eggs, it can result in eggs that have either an extra chromosome or a missing chromosome, which can lead to genetic disorders when fertilized.

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 the presence of an additional X chromosome. Individuals with Klinefelter syndrome may experience symptoms such as reduced testosterone levels, infertility, and physical traits like taller stature.

Turner Syndrome

Turner syndrome is a chromosomal disorder that affects females, characterized by the complete or partial absence of one X chromosome, resulting in a 45,X karyotype. This condition can occur when a normal male gamete fertilizes a female gamete that has lost an X chromosome due to nondisjunction. Turner syndrome can lead to various developmental issues, including short stature, ovarian dysfunction, and heart defects.

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From the following list, identify the types of chromosome changes you expect to show phenotypic consequences.

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