Difference Between Autosomes and Allosomes

Autosomes and Allosomes - Overview & Differences

Edited By Irshad Anwar | Updated on Nov 29, 2024 01:16 PM IST

Autosomes and allosomes are important genetic terms which define the variation that exists in the number of chromosomes carrying genetic traits and constitute an individual's genetic makeup. These terms are discussed in the chapter Principles of Inheritance and Variation, class 12. This article includes the difference between autosomes and allosomes, their functions, and their role in inheritance. Understanding autosomes and allosomes helps form the core base of genetics which is important for competitive exams like NEET where Biology is one of the major subjects asked.

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This Story also Contains

What are Autosomes?
What are Allosomes?
Difference Between Autosomes and Allosomes
Similarities between Autosomes and Allosomes
Importance of Autosomes and Allosomes in Biology
Autosomes and Allosomes in Genetics
Facts about Autosomes and Allosomes
Types of Questions and Weightage for Autosomes and Allosomes

What are Autosomes?

Autosomes are chromosomes that do not determine sex. In the human body, they exist in 22 pairs, carrying most of the genetic information on traits such as eye colour, blood type, and metabolism. They are the same in males and females and are determined by size and structure. General body functions and development mainly depend on autosomes. Changes in autosomes may cause several genetic disorders.

What are Allosomes?

Allosomes or sex chromosomes are the chromosomes responsible for the determination of sex in an organism. Human beings have one pair of allosomes bearing two X chromosomes in females and one X and one Y chromosome in males. Such chromosomes carry genes not only for sexual characters but also for other sex-linked traits like colour blindness and haemophilia.

Difference Between Autosomes and Allosomes

Autosomes and allosomes are one of important topics among the differences and comparison articles in Biology. The table below describes the major differences between autosomes and allosomes:

Parameter	Autosomes	Allosomes
Number	22 pairs in humans.	1 pair in humans.
Role in Sex Determination	Not involved in sex determination.	Determines sex (XX in females, XY in males).
Presence	Same in both sexes.	Differs between sexes.
Genetic Role	Carries genes for general traits and metabolism.	Carries genes for sex-linked traits.
Inheritance Pattern	One from each parent, equally inherited.	Males inherit X or Y from their father, and X from their mother.
Variation Among Species	The number remains similar in most species.	Varies widely among species.
Mutation Effects	Mutations can lead to metabolic or structural disorders.	Mutations often lead to sex-linked disorders (e.g., colour blindness).
Chromosome Size	Generally larger and more stable.	Y chromosome is smaller and more prone to mutations.

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Similarities between Autosomes and Allosomes

Autosomes and allosomes are components of chromosomes.
They can be located in the genome of an organism.
In both, DNA and proteins are present.
They include details about a person's forebears.
They both possess genes.
They are found in pairs.
Anomalies in both types of chromosomes can lead to many genetic diseases.

Importance of Autosomes and Allosomes in Biology

The concept of autosome and allosome is important for students studying biology at class 12 and NEET levels in understanding the concepts of inheritance, genetic variation, and disorders. Thus, autosomal and allosomal knowledge form the basis of advanced topics that include chromosomal abnormalities, sex-linked inheritance, and genetic counselling.

Autosomes and Allosomes in Genetics

Autosomes and allosomes complement each other in genetics. While autosomes are involved in determining the general phenotype as they carry genes responsible for most traits, allosomes are significant in determining sex and hence associate characters. In this sense, it is also crucial in explaining why some genetic disorders like Turner syndrome or Klinefelter affect the allosomes and hence influence sex characteristics.

Facts about Autosomes and Allosomes

Autosomes are chromosomes that are devoid of any sex-specific genes.
Due to the homomorphism of autosomes, the centromere is located in the same place.
On autosomes, there are 200–2000 different genes. In humans, chromosome 1 is the biggest chromosome and contains over 2800 genes.
The majority of chromosomes in a genotype are autosomes.
On the chromosomes of both men and women exist sex-determining genes (but may also carry many other genes that have nothing to do with sex).
Due to heteromorphic sex chromosomes, the position of the centromere varies between male and female chromosomes. Both male and female chromosomes have the same location for the centromere.

Types of Questions and Weightage for Autosomes and Allosomes

The table below indicates the weightage and types of questions asked from autosomes and allosomes in different exams:

Exam Type	Types of Questions	Weightage
CBSE Exams	Short answer questions on the differences between autosomes and allosomes, with examples	3-5%
NEET	Multiple-choice questions (MCQs) on the structure and roles of autosomes and allosomes	2-3%
AIIMS	Assertion and reasoning questions on inheritance patterns and functions of autosomes and allosomes	2-3%
Nursing Exams	True/False questions on the number, role, and impact of autosomes and allosomes	1-3%

Read More:

Mendelian Genetics	Gene Interaction
Epistasis	Pleiotropy
Acquired and Inherited Traits	Gene Mapping

Frequently Asked Questions (FAQs)

1. How do autosomal chromosomes function?

Autosomal chromosomes function by carrying genes that encode for a wide range of traits and metabolic processes essential for an organism's development and maintenance. They are involved in various cellular functions, including growth, immune response, and metabolic activities. Autosomal chromosomes operate through the expression of these genes, influencing physical traits and physiological functions without determining the sex of the individual.

2. Do Women possess 46 autosomes?

Yes, women possess 46 chromosomes in total, which include 22 pairs of autosomes and one pair of sex chromosomes (XX). Therefore, women have 44 autosomes (22 pairs) and 2 sex chromosomes, making up the complete set of 46 chromosomes.

3. Does the XXY chromosome exist?

Yes, the XXY chromosome configuration does exist. This chromosomal pattern is known as Klinefelter syndrome, a genetic condition that affects males. Individuals with Klinefelter syndrome typically have one extra X chromosome, resulting in a total of 47 chromosomes (44 autosomes and 3 sex chromosomes: XXY). This condition can lead to various physical and developmental traits, including reduced testosterone levels, gynecomastia and fertility issues.

4. What are allosomes?

Allosomes are sex chromosomes that are different in shape, size, or behaviour from a typical autosome. A typical pair of allosomes is the human sex chromosomes. In contrast to sperm, which can include either X or Y chromosomes, the X chromosome is present in the ovum.

5. Are Autosomes haploid or diploid?

Haploid and diploid cells both include autosomes. Chromosomes called autosomes don't affect sex determination. Human body cells are diploid, which means they contain two sets of autosomes—one from the mother and one from the father.