Non-mendelian inheritance - Epigenetic inheritance: dosage compensation

11 important questions on Non-mendelian inheritance - Epigenetic inheritance: dosage compensation

What is dosage compensation?

Dosage compensation refers to the phenomenon in which the level of expression of many genes on the sex chromosomes is similar in both sexes even though males and females have a different complement of sex chromosomes.

How do female mammals equalize the expression of X-linked genes?

By turning off one of their two X chromosomes, which is called X-chromosome inactivation.

Why is the Barr body more brightly staining in a cell nucleus than the other chromosomes?

The Barr body is more compact.
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What is the Lyon hypothesis?

The Lyon hypothesis is the mechanism of X-chromosome inactivation (XCI).

At which stage of development does XCI initially occur?

X-chromosome inactivation initially occurs during embryonic development.

How can XCI explain a variegated coat pattern?

Initially both X chromosomes are active. However, at an early stage of embryonic development, one of the two X chromosomes is randomly inactivated in each somatic cell and becomes a Barr body.

Which of the phases of XCI occurs in an adult?

Only the phase of maintenance occurs in a female adult.

What are the phases of XCI?

The phases of XCI are:
  • Initiation;
  • Spreading;
  • Maintenance.

What happens in the initiation phase of XCI? And when does it occur?

During initiation, which occurs in embryonic development, one of the X chromosomes remains active, and the other is chosen to be inactivated.

What happens during the spreading phase of XCI?

During the spreading phase, the chosen X chromosome is inactivated. The spreading phase is so named because inactivation begins at the Xic and spreads in both directions along the X chromosome.

What is the maintenance phase of XCI?

The maintenance phase of XCI occurs from embryonic development through adult life. The inactivated X chromosome is maintained as such during subsequent cell divisions.

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