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Dosage Compensation

Dosage Compensation

In animals, gender is determined by the number and type of sex chromosome. For example, human females have two X chromosomes, and males have one X and one Y chromosome, whereas C.elegans with one X chromosome is a male, and the one with two X chromosomes is a hermaphrodite.
In addition to sexual development, the X chromosome has genes involved in autosomal functions such as brain development and the immune system. Therefore, males and females with distinct numbers of X chromosomes will have...

X and Y Chromosomes

X and Y Chromosomes

Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A human female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...

X-Inactivation

X-Inactivation

The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.

X-inactivation

X-inactivation

The human X chromosome contains over ten times the number of genes as in the Y chromosome. Since males have only one X chromosome, and females have two, one might expect females to produce twice as many of the proteins, with undesirable results.

X-linked Traits

X-linked Traits

In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”.

X-linked Traits

X-linked Traits

In most mammalian species, females have two X sex chromosomes and males have an X and Y. As a result, mutations on the X chromosome in females may be masked by the presence of a normal allele on the second X. In contrast, a mutation on the X chromosome in males more often causes observable biological defects, as there is no normal X to compensate. Trait variations arising from mutations on the X chromosome are called “X-linked”.

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Related Experiment Video

Updated: Jul 9, 2026

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

Published on: December 10, 2012

X-Chromosome dosage compensation.

Barbara J Meyer¹

¹Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3204, USA. bjmeyer@berkeley.edu

Wormbook : the Online Review of C. Elegans Biology

|December 1, 2007

Summary

The dosage compensation complex (DCC) in C. elegans binds both X chromosomes in hermaphrodites, reducing gene expression by half. This process utilizes ancient condensin proteins and X-recognition elements for epigenetic regulation.

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Chromosome Replicating Timing Combined with Fluorescent In situ Hybridization

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Published on: June 14, 2014

Area of Science:

Genetics
Molecular Biology
Epigenetics

Background:

Sex determination in mammals, flies, and worms relies on X chromosome dosage.
Dosage compensation equalizes X-linked gene expression between sexes.
The C. elegans dosage compensation complex (DCC) targets X chromosomes in hermaphrodites.

Purpose of the Study:

To elucidate the mechanisms of X chromosome dosage compensation in C. elegans.
To understand how the DCC is targeted to X chromosomes.
To explore the relationship between DCC and condensin complexes.

Main Methods:

Genetic pathway analysis for sex determination and dosage compensation.
Biochemical characterization of the dosage compensation complex (DCC).
Identification of X-chromosome recognition elements.

Main Results:

The DCC binds both X chromosomes in hermaphrodites, reducing transcript levels by 50%.
DCC shares components with the conserved 13S condensin complex.
X-chromosome recognition elements recruit and spread the DCC, establishing epigenetic regulation.

Conclusions:

C. elegans dosage compensation involves ancient proteins repurposed for gene regulation.
Epigenetic spreading of the DCC ensures global X chromosome regulation.
Distinct pathways control sex determination and dosage compensation post-chromosome counting.