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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...

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....

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-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”.

Pedigree Analysis

Pedigree Analysis

Sex Linked Disorders

Sex Linked Disorders

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Related Experiment Video

Updated: Apr 16, 2026

Sexual Transmission of American Trypanosomes from Males and Females to Naive Mates

Sexual Transmission of American Trypanosomes from Males and Females to Naive Mates

Published on: January 27, 2019

Biological Sex Differences in the US-CTEPH-R.

Meghan M Cirulis¹, William R Auger², Raymond L Benza³

¹Department of Pulmonary and Critical Care Medicine, Intermountain Health, Murray, UT.

Annals of the American Thoracic Society

|April 14, 2026

Summary

This summary is machine-generated.

Males and females exhibit distinct chronic thromboembolic pulmonary hypertension (CTEPH) phenotypes. While overall survival is similar, females experience worse health-related quality of life and function post-pulmonary thromboendarterectomy.

Keywords:

CTEPH biological sex distal CTEPH pulmonary thromboendarterectomy sex differences sex paradox

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Area of Science:

Cardiopulmonary Medicine
Pulmonary Hypertension Research
Sex Differences in Disease

Background:

Biological sex influences cardiopulmonary conditions, with known sex paradoxes in pulmonary arterial hypertension.
Sex differences in chronic thromboembolic pulmonary hypertension (CTEPH) are less understood compared to pulmonary arterial hypertension (PAH).

Purpose of the Study:

To investigate and characterize sex differences in patients diagnosed with CTEPH in the United States.
To explore how biological sex impacts CTEPH presentation, treatment, and outcomes.

Main Methods:

Utilized data from the multicenter United States CTEPH Registry, collecting data every six months for 48 months.
Compared male and female characteristics using descriptive analyses and regression modeling, adjusting for age and BMI.
Performed survival analysis using Cox proportional hazards modeling.

Main Results:

Females had higher BMI, while males were more likely to have a history of deep vein thrombosis.
Males demonstrated better baseline PH-specific health-related quality of life (HRQoL), WHO functional class, and six-minute walk distance.
Males were less likely to have distally located disease or inoperable CTEPH; however, no significant difference in overall survival was observed between sexes.

Conclusions:

Distinct CTEPH phenotypes exist between males and females, potentially influencing pulmonary thromboendarterectomy (PTE) access and feasibility.
Sex-associated disparities exist in the disease experience and HRQoL for CTEPH patients.
Further investigation is warranted to understand differential impacts on HRQoL and disease experience.