Chromosomes are thread-like structures present in the nucleus of both plant and animal cells. This cell organelle functions by carrying genetic information from one generation to another, and they play a primary role in heredity, cell division, variation, mutation, repair and regeneration.
Chromosomes were first discovered by Walther Flemming in 1882. Later in 1888, W. Waldeyer, a German anatomist well known for the neuron theory and anatomical structures of the human body, coined the term chromosome.
Chromosomes are passed to offspring from their parents over generations and are mainly composed of two components – proteins and a single molecule of deoxyribonucleic acid – DNA.
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X and Y chromosomes
The X and Y chromosomes are also referred to as the sex chromosomes, as they determine the sex of an individual.
Every living species, from plants to animals, has a set number of chromosomes.
This number is constant for all the cells and the total number varies with the species. We, humans, have 46 or 23 pairs of chromosomes. Among these, 44 or 22 pairs are autosomes, and the 23rd pair of chromosomes (X and Y) are called the sex chromosome or allosomes.
Also Refer: Difference between Autosomes and Allosomes
These sex chromosomes determine the sex of a baby. Each sex chromosome is inherited from each parent.
In humans, females have two copies of the ‘X’ chromosome inherited from each parent, in which only one is active. In contrast, males have one ‘X’ and one ‘Y’ chromosome and always inherit the X chromosome from their mother and the Y chromosome from their father, in which both the sex chromosomes are active.
Also Refer: Chromosomal Abnormalities in Humans
Let’s learn the differences between X and Y chromosomes.
X and Y chromosomes – Comparisons
| Longer than the Y-chromosome. | Shorter than the X-chromosome. |
| The centromere is precisely located in the centre of the chromosomes. Hence, it is called metacentric. | The centromere is present at one end of the chromosomes. Hence, it is called acrocentric. |
| Present in both males and females. | Present only in males. |
| Females have two copies of X chromosomes and males have only one copy of X chromosome. | Males have only one copy of the Y chromosome and females lack the Y chromosome. |
| Contains a larger amount of genes. | Contains a lesser amount of genes. |
| Contains a larger amount of DNA. | Contains a lesser amount of DNA. |
| Genes show a criss-cross type of inheritance. | Genes show a straight type of inheritance. |
| Contains a large amount of euchromatin. | Contains a lesser amount of euchromatin. |
| Contains a lesser amount of heterochromatin. | Contains a large amount of heterochromatin. |
| Only one X chromosome is active and is involved in the development of the Barr body, formation of eggs and other characteristics of the females. | Comprises of a unique male-determining gene and is involved in the development of testes, formation of sperm and other characteristics of the males. |
Also refer: Difference between Gene and Chromosome
This article concludes the introduction to chromosome, X and Y chromosomes and their differences.
Stay tuned to BYJU’S Biology to learn more in detail about the chromosome, its structure, functions, types and features.
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