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
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
6. Chromosomal Variation
Chromosomal Mutations: Aneuploidy
2:07 minutes
Problem 18b
Textbook Question
Textbook QuestionCan the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene? Why, or why not?
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lyon Hypothesis
The Lyon hypothesis, proposed by Mary Lyon in 1961, states that in female mammals, one of the two X chromosomes is randomly inactivated during early embryonic development. This process, known as X-inactivation, ensures dosage compensation between males (XY) and females (XX) for X-linked genes. The inactivated X chromosome forms a Barr body and is largely transcriptionally silent, which can affect the expression of X-linked traits.
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Translation:Wobble Hypothesis
X-linked Inheritance
X-linked inheritance refers to the pattern of inheritance for genes located on the X chromosome. In females, who have two X chromosomes, the effects of X-linked alleles can be masked by the presence of a second allele. In contrast, males, having only one X chromosome, express whatever allele is present, making X-linked traits more apparent in males. This is crucial for understanding how traits like G6PD deficiency are inherited and expressed.
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X-Inactivation
Homozygosity in X-linked Genes
Homozygosity in the context of X-linked genes occurs when an individual has two identical alleles for a gene located on the X chromosome. In a human female who is homozygous for one allele of the G6PD gene, both X chromosomes carry the same allele, meaning that X-inactivation would not affect the expression of the G6PD gene. Therefore, testing the Lyon hypothesis in this scenario is not feasible, as there would be no variability in expression to observe.
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Sex-Linked Genes
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