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Ch. 7 - Sex Determination and Sex Chromosomes
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of GeneticsISBN: 9780135564776Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoKlug 12th EditionCh. 7 - Sex Determination and Sex ChromosomesProblema 15
Capitolo 7, Problema 15

What is a Barr body, and where is it found in a cell?

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1
Understand that a Barr body is a dense, inactivated X chromosome found in the nuclei of female mammalian cells.
Recall that females have two X chromosomes, but to balance gene expression with males (who have one X chromosome), one X chromosome is largely inactivated during early development.
Recognize that this inactivated X chromosome condenses into a compact structure called the Barr body, which is visible under a microscope as a dense spot in the nucleus.
Note that the Barr body is typically located at the periphery of the nucleus within the cell.
Summarize that the Barr body represents a mechanism of dosage compensation to equalize X-linked gene expression between males and females.

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Barr Body

A Barr body is an inactivated X chromosome found in the nuclei of female mammalian cells. It appears as a dense, compact structure and represents the silenced X chromosome to balance gene dosage between males and females.
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Other Chromatin Modifications

X-Chromosome Inactivation

X-chromosome inactivation is a process in female mammals where one of the two X chromosomes is randomly silenced during early embryonic development. This ensures dosage compensation so that females, like males, have one functional copy of X-linked genes.
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X-Inactivation

Cellular Localization of Barr Body

The Barr body is located in the nucleus of somatic cells, typically attached to the inner nuclear membrane. It is visible under a microscope as a dense spot and is absent in male cells, which have only one X chromosome.
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Post Translational Modifications
Pratica correlata
Domanda del libro di testo

It has been suggested that any male-determining genes contained on the Y chromosome in humans cannot be located in the limited region that synapses with the X chromosome during meiosis. What might be the outcome if such genes were located in this region?

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Domanda del libro di testo

Indicate the expected number of Barr bodies in interphase cells of individuals with Klinefelter syndrome, Turner syndrome, and karyotypes 47, XYY, 47, XXX, and 48, XXXX.

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Domanda del libro di testo

Define the Lyon hypothesis.

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Can 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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Domanda del libro di testo

Assume that on rare occasions the attached X chromosomes in female gametes become unattached. Based on the parental phenotypes in Problem 12, what outcomes in the F₁ generation would indicate that this has occurred during female meiosis?

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Domanda del libro di testo

An attached-X female fly, XXY, expresses the recessive X-linked white-eye mutation. It is crossed to a male fly that expresses the X-linked recessive miniature-wing mutation. Determine the outcome of this cross in terms of sex, eye color, and wing size of the offspring.

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