The key difference between autosomes and sex chromosomes is that the autosomes contain genes that are responsible for the determination of somatic characteristics while the sex chromosomes contain genes that determine sex and sex-related characteristics of an organism.
The most important structures in a cell during the cell division are the chromosomes, which contain DNA. This is because they are responsible for the transmission of the hereditary information from one generation to the next. There are two types of chromosomes such as autosomes and sex chromosomes. Sex chromosomes are important in sex determination.
CONTENTS
1. Overview and Key Difference
2. What are Autosomes
3. What are Sex Chromosomes
4. Similarities Between Autosomes and Sex Chromosomes
5. Side by Side Comparison – Autosomes vs Sex Chromosomes in Tabular Form
6. Summary
What are Autosomes?
Any chromosome, which is not a sex chromosome, is an autosome. There are 22 pairs of autosomes in humans. Each autosome contains a large number of genes arranges in a definite sequence. In these homologous pairs, the 2 chromosomes are of the same length. However, in these, the position of the centromere is the same.
Figure 01: Autosomes
Moreover, mitosis is the process by which all these chromosomes duplicate and give one copy of each chromosome to each of the daughter cells. Therefore, this ensures that all somatic cells of an organism’s body carry an identical set of genes.
What are Sex Chromosomes?
Humans have 23 pairs of chromosomes. Among them, one pair is sex chromosomes. Other 22 are autosomes. Thus, sex chromosomes are of 2 types; X and Y. In these, Y is smaller. Hence, X and Y are partially homologous. However, they pair up and segregate into daughter cells during meiosis. Males have X and Y combination while females have X and X combination. Moreover, all female gametes carry only one X chromosome. Male gametes may carry either X or Y. The number carrying X is equal to the number carrying Y. If an ovum unites with a sperm carrying X, the result is a female XX. If an ovum fertilizes with a sperm carrying Y, the result is a male XY.
Figure 02: Sex Chromosomes
Sex-linked characters show deviations from Mendel’s laws. All the genes carried by X chromosomes do not determine sexuality. Many of the genes have other functions similar to genes carried in autosomes. Sex-linked inheritance shown by genes carried with X chromosomes is not represented in Y chromosomes. These genes normally have recessive alleles, and they show recessive mutations. However, these defective alleles are very rare in the human population. Hence, they do not express in females as they carry 2X chromosomes. Heterozygous females are carriers, and they may pass these genes onto their sons. Then they will be expressed in males because they have only one X chromosome.
What are the Similarities Between Autosomes and Sex Chromosomes?
- Autosomes and sex chromosomes contain DNA and proteins.
- They located in the human genome inside the nucleus.
- They have genes.
- Hence, they determine the characteristics of the organism.
- They exist as pairs.
- Both segregate during the cell division.
- They are responsible for inheritance.
What is the Difference Between Autosomes and Sex Chromosomes?
There is a total of 46 chromosomes in the human genome. Among them, 44 are autosomes that are responsible for somatic characteristics of an organism. The other 2 chromosomes are sex chromosomes that determine sex and sex-related characteristics of an organism. This is the key difference between autosomes and sex chromosomes. Furthermore, the height and the centromere position are the same between homologous chromosomes of the autosomes while they may differ between the sex chromosome pair.
The below infographic presents more details on the difference between autosomes and sex chromosomes.
Summary – Autosomes vs Sex Chromosomes
Autosomes are the homologous pairs of chromosomes in the human genome that determine the somatic characteristics of an organism. Sex chromosomes determine the sex of the organism. They are partially homologous. Out of 23 pairs, 22 are autosomes while one pair is sex chromosomes. This is the difference between autosomes and sex chromosomes.
Reference:
1.Nature News, Nature Publishing Group. Available here
2.Szalay, Jessie. “Chromosomes: Definition & Structure.” LiveScience, Purch, 8 Dec. 2017. Available here
Image Courtesy:
1.”10188534666″ by Zappys Technology Solutions (CC BY 2.0) via Flickr
2.”Human male karyotpe high resolution – Sex chromosomes” By National Human Genome Research Institute (Public Domain) via Commons Wikimedia