Autosomes and Allosomes - Overview & Differences

Autosomes and allosomes are important genetic terms which define the variation that exists in the number of chromosomes carrying genetic material of an individual. In humans, there are a total of 23 pairs of chromosomes, out of which 22 pairs are autosomes and the remaining 1 pair is known as allosomes or sex chromosomes. Autosomes are responsible for determining most of the traits such as eye color, height, skin color, etc.

This Story also Contains

1. What are Autosomes?
2. What are Allosomes?
3. Difference Between Autosomes and Allosomes
4. Similarities between Autosomes and Allosomes
5. Importance of Autosomes and Allosomes in Biology
6. Autosomes and Allosomes in Genetics
7. Facts about Autosomes and Allosomes
8. MCQs on Autosomes and Allosomes

Allosomes help in sex determination and are different in males and females. Any mistake in the number or structure of these chromosomes lead to chromosomal abnormalities, such as Turner syndrome, Klinefelter syndrome, etc. Understanding their roles helps in identifying genetic disorders and studying inheritance patterns.

What are Autosomes?

Autosomes are chromosomes that carry most of the genetic information on traits such as eye colour, blood type, and metabolism. In the human body, they exist in 22 pairs and do not determine sex. 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 human 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, two X chromosomes in females and one X and one Y chromosome in males. Such chromosomes carry genes for sexual characters as well as other sex-linked traits like colour blindness and haemophilia.

Difference Between Autosomes and Allosomes

Autosomes and allosomes are two types of chromosomes in the human body. While autosomes are involved in determining body traits, allosomes are responsible for sex determination. Understanding the difference between these two is important in the study of genetics. The table below describes the major differences between autosomes and allosomes:

Similarities between Autosomes and Allosomes

The similarities between autosomes and allosomes highlight their common structural and functional roles in the human genome. Both are types of chromosomes that are involved in inheritance. The following points highlight the similarities between the two:

• 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 the ancestors of individuals.

• 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 understanding the concepts of inheritance, genetic variation, and disorders. Thus, knowledge of autosomal and allosomal 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 by carrying genes that determine both physical traits and biological functions. While autosomes are involved in determining the general phenotype as they carry genes responsible for most traits, allosomes are significant in determining sex. It is also crucial to understand their function, as it explains why some genetic disorders like Turner syndrome or Klinefelter affect the allosomes and hence influence sex characteristics. Their analysis is important in diagnosing chromosomal abnormalities and genetic research.

Facts about Autosomes and Allosomes

Here are some interesting facts that highlight the characteristics of autosomes and allosomes. These facts can help understand how chromosomes influence traits, and variation. They also provide information about genetic structure and function in organisms.

• 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.

• There are 200–2000 different genes on autosomes. In humans, chromosome 1 is the biggest chromosome and contains over 2800 genes.

• The majority of chromosomes in a genotype are autosomes.

• The chromosomes of both male and female 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.

MCQs on Autosomes and Allosomes

Q1. In the following questions, a statement of assertion (A) is followed by a statement of reason (R)

(1) If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark A

(2) If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark B

(3) If the Assertion is a true statement but Reason is false, then mark C

(4) If both Assertion and Reason are false statements, then mark D

Assertion: The sex of an individual is determined by their sex chromosomes.

Reason: Males have one X and one Y chromosome, while females have two X chromosomes.

1. Both Assertion (A) and Reason (R) are the true and Reason (R) is a correct explanation of Assertion (A).

2. Both Assertion (A) and Reason (R) are the true but Reason (R) is not a correct explanation of Assertion (A).

3. Assertion (A) is true and Reason (R) is false.

4. Assertion (A) is false and Reason (R) is true.

Correct answer: Both Assertion (A) and Reason (R) are the true and Reason (R) is a correct explanation of Assertion (A).

Explanation:

The sex of an individual is determined by the sex chromosomes they inherit from their parents. In humans, females have two copies of the X chromosome (XX), while males have one X chromosome and one Y chromosome (XY).During fertilization, a sperm carrying either an X or Y chromosome can fuse with an egg carrying an X chromosome, resulting in the formation of a female (XX) or male (XY) embryo, respectively.

Therefore, it is correct to say that the sex of an individual is determined by their sex chromosomes. Additionally, it is correct to say that males have one X and one Y chromosome, while females have two X chromosomes. So, in summary, the sex of an individual is determined by their sex chromosomes, males have one X and one Y chromosome, while females have two X chromosomes.

Hence, the correct option is 1) Both Assertion (A) and Reason (R) are true and Reason (R) is a correct explanation of Assertion (A).

Q2. The total number of autosomes will be the same in:

1. Male and female human

2. Male and female birds

3. Male and female drosophila

4. Male and female grasshopper.

5. Only I, II, and III

6. Only I, II, and IV

7. Only II, III, and IV

8. I, II, III, and IV

Correct answer: 4. I, II, III, and IV

Explanation:

Autosomes are the chromosomes that are not involved in determining the sex of an organism. All individuals of the same species have the same number of autosomes, whether they are male or female.

Hence, the correct answer is option 4) I, II, III, and IV.

Also Read:

• MCQs on Genetics

• 23 Chromosomes and their Functions

• Molecular Basis of Inheritance