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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...

Sex-linked Disorders

Sex-linked Disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

The Y Chromosome Determines Maleness

The Y Chromosome Determines Maleness

The Y chromosome is a sex chromosome found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human males have one X chromosome and one Y chromosome. In these organisms, the presence or absence of the Y chromosome determines the development of male traits.
Evolution
Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size....

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

The Ratio of X Chromosome to Autosomes

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...

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...

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Related Experiment Video

Updated: Aug 14, 2025

Exploring X Chromosomal Aberrations in Ovarian Cells by Using Fluorescence In Situ Hybridization

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Published on: April 7, 2023

Sex Chromosome Rearrangement Associated With Hormonal Abnormalities and Gender Dysphoria.

Zachary A Cordner, Weiyi Mu, Chester W Schmidt

Journal of Psychiatric Practice

|January 17, 2023

Summary

This case study highlights a gender nonbinary individual with lifelong gender dysphoria, revealing a novel sex chromosomal rearrangement and hormonal abnormalities. This underscores the need for psychiatric and gender-focused care in sex chromosome disorders.

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Area of Science:

Neuropsychiatry
Genetics
Endocrinology

Background:

Sex chromosome abnormalities and steroid metabolism disorders are well-understood in endocrinology and reproductive health.
However, their impact on neuropsychiatric development, gender identity, incongruence, and dysphoria remains less explored.

Observation:

A 21-year-old, male-assigned at birth, gender nonbinary individual presented with lifelong gender dysphoria.
The patient exhibited a complex sex chromosomal rearrangement and associated hormonal abnormalities.

Findings:

A novel genetic alteration was identified in the patient.
The identified abnormalities may contribute to the patient's gender dysphoria and related history.

Implications:

This case emphasizes the critical need for integrating psychiatric and gender-specific evaluations for individuals with sex chromosome abnormalities.
Further research is warranted to understand the complex interplay between genetics, hormones, and gender identity in these populations.