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

Sex Chromosome

Genetics

3. Extensions to Mendelian Inheritance

Sex Chromosome

Previous problemNext problem

1:17 minutes

Problem 10

Textbook Question

How many Barr bodies are found in a normal human female nucleus? In a normal male nucleus?

Verified step by step guidance

Understand what a Barr body is: it is an inactivated X chromosome found in the nuclei of cells in females, serving as a mechanism for dosage compensation between males and females.

Recall that normal human females have two X chromosomes (XX), while normal males have one X and one Y chromosome (XY).

Apply the formula for the number of Barr bodies: Number of Barr bodies = (Number of X chromosomes) - 1.

For a normal female (XX), calculate the number of Barr bodies as

X = 2

, so Barr bodies =

2 - 1 = 1

For a normal male (XY), calculate the number of Barr bodies as

X = 1

, so Barr bodies =

1 - 1 = 0

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Barr Body

A Barr body is an inactivated X chromosome found in the nuclei of female cells. It appears as a dense, dark-staining spot and represents the mechanism of dosage compensation to balance gene expression between males and females.

X Chromosome Inactivation

X chromosome inactivation is the process by which one of the two X chromosomes in females is randomly silenced during early embryonic development. This ensures that females, like males, have one functional copy of the X chromosome in each cell.

Sex Chromosome Composition in Humans

Normal human females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). This difference determines the number of Barr bodies: females typically have one Barr body, and males have none.

Watch next

Master Sex Determination with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Textbook Question

Describe the major difference between sex determination in Drosophila and in humans.

3277

views

Textbook Question

How do mammals, including humans, solve the 'dosage problem' caused by the presence of an X and Y chromosome in one sex and two X chromosomes in the other sex?

897

views

Textbook Question

The phenotype of an early-stage human embryo is considered sexually indifferent. Explain why this is so even though the embryo's genotypic sex is already fixed.

693

views

Textbook Question

What specific observations (evidence) support the conclusions about sex determination in Drosophila and humans?

478

views

Textbook Question

An insect species is discovered in which the heterogametic sex is unknown. An X-linked recessive mutation for reduced wing (rw) is discovered. Contrast the F₁ and F₂ generations from a cross between a female with reduced wings and a male with normal-sized wings when the female is the heterogametic sex.

Consider the case where a mutation occurs that disrupts translation in a single human mitochondrion found in the oocyte participating in fertilization. What is the likely impact of this mutation on the offspring arising from this oocyte?

416

views

Textbook Question

What is the basis for homology among chromosomes?

516

views

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap