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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

3. Extensions to Mendelian Inheritance

X-Inactivation

Genetics

3. Extensions to Mendelian Inheritance

X-Inactivation

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Multiple Choice

All female mammals have one active X chromosome per cell instead of two. What causes this phenomenon?

Random inactivation of one X chromosome in each cell during early embryonic development

Deletion of one X chromosome in all somatic cells

Suppression of X-linked gene expression by autosomal genes

Selective activation of both X chromosomes in every cell

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Verified step by step guidance

Understand that female mammals have two X chromosomes, but only one is active in each somatic cell to balance gene expression with males, who have only one X chromosome.

Recognize that this process is called X-chromosome inactivation, which ensures dosage compensation between males and females.

Know that X-chromosome inactivation occurs early in embryonic development and is random, meaning either the maternal or paternal X chromosome can be inactivated in each cell.

Realize that the inactivated X chromosome condenses into a structure called a Barr body, effectively silencing most of its genes.

Conclude that the phenomenon is caused by the random inactivation of one X chromosome in each cell during early embryonic development, not by deletion or suppression by autosomal genes.