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

3. Extensions to Mendelian Inheritance

X-Inactivation

Genetics

3. Extensions to Mendelian Inheritance

X-Inactivation

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Multiple Choice

Which of these sequences plays a critical role in Barr body formation?

XIST gene

Lac operon

SRY gene

TATA box

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Verified step by step guidance

Understand the concept of a Barr body: it is an inactivated X chromosome found in female mammals, which helps balance gene dosage between males (XY) and females (XX).

Recall that Barr body formation involves the process of X chromosome inactivation, where one of the two X chromosomes in females becomes transcriptionally silent.

Identify the key genetic element responsible for initiating X chromosome inactivation: the XIST gene, which produces a long non-coding RNA that coats the X chromosome to be inactivated.

Recognize that other options like the Lac operon (a bacterial gene regulation system), SRY gene (sex-determining region on the Y chromosome), and TATA box (a promoter sequence) are unrelated to Barr body formation.

Conclude that the XIST gene is the critical sequence involved in Barr body formation because it triggers the silencing of one X chromosome in females.