Difference Between Autosomes and Allosomes

The key difference between autosomes and allosomes is that the autosomes are somatic chromosomes that involve in determining the somatic characteristics other than sex determination while the allosomes are the sex chromosomes that determine the sex and sex-related characteristics of an organism.

Chromosomes are a thread like structures made from nucleic acids and proteins. We can find chromosomes in the cell nucleus of eukaryotes. In prokaryotes, chromosomes reside in the cytoplasm. Chromosomes carry the genetic information of the organism in the form of genes. The human genome contains a total of 23 pairs of chromosome. Among them, there are 22 pairs of autosomes and one pair of allosomes. Autosomes are the typical chromosomes while allosomes are the atypical chromosomes.

CONTENTS

1. Overview and Key Difference
2. What are Autosomes
3. What are Allosomes
4. Similarities Between Autosomes and Allosomes
5. Side by Side Comparison – Autosomes vs Allosomes in Tabular Form
6. Summary

What are Autosomes?

Autosomes also known as somatic chromosomes are the chromosomes that carry genes that determine the somatic characteristics and therefore, do not have any influence on determining the sex of the organism. Majority of the chromosomes in the genome of an organism is autosomes.

The human genome contains a total of 44 autosomes (22 pairs). They are numbered from 1 to 22. They are homologous chromosomes, and they have a similar appearance and structure. The atDNA or the auDNA is the total DNA in autosomes.

What are Allosomes?

Allosomes are the chromosomes that differ from ordinary chromosomes (autosomes) by size, form, shape, function and behaviour. They are the sex chromosomes. They are atypical chromosomes. Furthermore, they are heterotypical chromosomes or heterochromosomes. Allosomes may differ from each other in pairs. The human genome has one pair of allosomes. In females, the sex chromosome pair is XX while in males it is XY. X chromosomes appear same while Y chromosome is smaller than the X chromosome. Due to this fact, females contain 23 pairs of homologous chromosomes while males have only 22 pairs of homologous chromosomes. X chromosome comes from the egg cell whereas X or Y chromosomes come from male sperm.

Allosomes determine the sex of the offspring produced via the sexual reproduction. The genes located in the allosomes are sex-linked genes, so their inheritance and expression differ between males and females. Turner syndrome and Klinefelter syndrome are two sex chromosome related syndromes which arise due to chromosomal abnormalities.

What are the Similarities Difference Between Autosomes and Allosomes?

• Autosomes and allosomes are chromosomes.
• They are in the genome of an organism.
• Both comprise of DNA and proteins.
• They contain heredity information.
• Both of them have genes.
• They exist in pairs.
• Abnormalities lead to different genetic diseases.

What is the Difference Between Autosomes and Allosomes?

Total chromosomes in the genome can be divided into two categories; autosomes and allosomes. Autosomes are the somatic chromosomes that determine the somatic characteristics. Whereas, the allosomes are the sex chromosomes that determine sex and the sex-related characteristics. This is the key difference between autosomes and allosomes. Moreover, the human genome has 22 pairs of homologous autosomes. But, in the case of allosomes, the females have one homologous pair of allosomes while the males have one nonhomologous pair of allosomes.

The below infographic presents the difference between autosomes and allosomes in tabular form.

Summary – Autosomes vs Allosomes

Autosomes and allosomes are chromosomes that consist of the genetic information of an organism. Autosomes occupy the majority of the chromosomes in the genome. They determine the somatic characteristics of an organism. Allosomes involve in the sex determination of an offspring produced by sexual reproduction. Furthermore, the autosomes are homologous chromosomes. However, among the female and male allosomes, female allosomes are homologous while male allosomes are nonhomologous. This is the difference between autosomes and allosomes.

Reference:

1.“Allosome.” Egyptian Journal of Medical Human Genetics, Elsevier. Available here  

Image Courtesy:

1.”10188534666″ by Zappys Technology Solutions (CC BY 2.0) via Flickr
2.”Human male karyotpe high resolution – XY chromosome cropped” By Dietzel65 and RichardWeiss (CC0) via Commons Wikimedia