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Related Concept Videos

Dosage Compensation02:50

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...
The Ratio of X Chromosome to Autosomes02:45

The Ratio of X Chromosome to Autosomes

In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.  
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
Meiosis II01:57

Meiosis II

Meiosis II is the second and final stage of meiosis. It relies on the haploid cells produced during meiosis I, each of which contain only 23 chromosomes—one from each homologous initial pair. Importantly, each chromosome in these cells is composed of two joined copies, and when these cells enter meiosis II, the goal is to separate such sister chromatids using the same microtubule-based network employed in other division processes. The result of meiosis II is two haploid cells, each containing...
Meiosis II02:02

Meiosis II

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for meiosis II are similar to mitosis, except that meiosis II occurs in haploid cells, whereas mitosis occurs in diploid cells.
The timing and cell division patterns of meiosis differ between males and females. In male meiosis, the centrosomes are part of the formation of the meiotic spindle. However, in oocytes, including that of humans, Drosophila,...

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Related Experiment Video

Updated: May 9, 2026

Manipulation of Ploidy in Caenorhabditis elegans
07:54

Manipulation of Ploidy in Caenorhabditis elegans

Published on: March 15, 2018

Sex determination: how worms count to two.

Ronald E Ellis1, Xiangmei Chen

  • 1Department of Molecular Biology, The UMDNJ School of Osteopathic Medicine, B303 Science Center, 2 Medical Center Drive, Stratford, NJ 08084, USA. ron.ellis@umdnj.edu

Current Biology : CB
|July 13, 2013
PubMed
Summary

Genetic competition between male and female genes determines sexual identity. Caenorhabditis elegans is the first animal found to use this century-old proposed mechanism.

Area of Science:

  • Genetics
  • Developmental Biology
  • Molecular Biology

Background:

  • Alfred Sturtevant's student, Calvin Bridges, proposed a theory of sex determination a century ago.
  • Bridges suggested that male genes on autosomes and female genes on the X chromosome compete to establish sexual identity.
  • This theory has remained largely untested in animal models until recent advancements.

Purpose of the Study:

  • To investigate the molecular mechanisms underlying sex determination in animals.
  • To test Bridges' century-old hypothesis regarding competing genetic factors in sexual identity.
  • To establish Caenorhabditis elegans as a model organism for studying this sex determination mechanism.

Main Methods:

  • Utilized advanced genetic and molecular techniques.

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Last Updated: May 9, 2026

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Measuring Embryonic Viability and Brood Size in Caenorhabditis elegans

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Published on: June 6, 2019

  • Conducted studies on the Caenorhabditis elegans model organism.
  • Analyzed gene expression and function related to sex determination pathways.

    • Main Results:

    • Confirmed the presence of a competitive genetic mechanism for sex determination in Caenorhabditis elegans.
    • Identified specific autosomal and X-linked genes involved in this competition.
    • Demonstrated that the balance of these genes dictates the sexual fate of the organism.

    Conclusions:

    • Caenorhabditis elegans provides the first animal evidence supporting Bridges' theory of sex determination.
    • This study elucidates a fundamental mechanism of sexual identity establishment.
    • The findings open new avenues for research into comparative genomics and evolution of sex determination.