Chromosomal Abnormalities

Chromosomes are a thread-like formation of protein, and nucleic acid found extensively in most living cells. These chromosomes are responsible for carrying genetic information and tend to play a vital role in formulating the genetic makeup of new generations.

Needless to say, any kind of abnormality or disruption in their functioning tends to hamper the healthy genetic formation or transfer of vital genetic data. 

Keeping this in mind, let’s proceed to find out more about chromosome abnormalities, their types and causes. Doing so, you will further understand the importance of chromosomes in general.

What are Chromosomal Abnormalities?

Chromosomal abnormalities are genetic disorders which occur due to a change in chromosomes or owing to the abnormal arrangement of chromosomes. 

Typically, there are several types of chromosomal abnormalities which can be categorised as either structural or numerical abnormality.

The most common types of numerical abnormalities are as follow –

  • Polyploidy 

This particular condition is widely observed in plants. Typically, it occurs when the chromosome count of a set increases owing to the malfunctioning of cytokinesis.

  • Aneuploidy

It typically arises due to increase or decreases of chromosomes. Notably, it is a result of abnormal segregation of genes. 

On the other hand, structural abnormalities arise due to breakage or incorrect arrangement of chromosomal segments. For example, ring chromosome abnormality can occur when a particular chromosome breaks twice, and then its broken ends join into a circular chromosome. 

Likewise, an isochromosome is formed when a chromosome’s arm goes missing, and the remaining one starts to duplicate. 

This image below shows the common numerical and structural chromosomal aberrations.

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DIY: What is chromosome disorder? Provide suitable examples.

Types of Chromosomal Disorders

Some of the most common examples of chromosomal abnormalities include Down syndrome, Turner syndrome and Klinefelter syndrome. Details of such disorders are mentioned below.

  1. Down Syndrome

This particular chromosomal abnormality occurs due to an additional chromosome 21, which in turn occurred due to abnormal cell division. In a broader sense, it can be divided into three types – translocation, trisomy 21 and mosaicism.

It tends to hamper the physical characteristics and cognitive development in individuals. Also, the most noticeable symptoms of Down syndrome include small height, short neck, low muscle tone, eyes which slant upwards, etc. 

  1. Turner Syndrome

In this case, there is one X chromosome absent in females which decreases the chromosome count to 45 instead of 46. The prevalent symptoms of turner syndrome include sterility and absence of secondary sexual traits.

Other than that, heart disorders, high blood pressure, skeletal abnormalities and kidney ailments are other prominent indicators of turner syndrome.

  1. Klinefelter syndrome

An extra X chromosome in males is the reason behind the occurrence of Klinefelter. Owing to this, the chromosome count stands at 47 instead of the standard 46. 

This chromosomal aberration tends to manifest in males in the form of absent or delayed puberty, sterility, development of breast, etc.  It is also said to affect the intellectual development in males. 

FAQ (Frequently Asked Questions)

1. What are chromosomal aberrations?

Ans. Chromosomal aberrations are the genetic disorder which occurred as a response to change in the number of the structural arrangement of chromosomes.

2. What are the seven types of abnormalities of chromosomes?

Ans. The seven types of abnormalities of chromosomes include – translocations, insertions, deletions, rings, mosaicism, mixoploidy and Aneuploidy.

3. What is Down syndrome?

Ans. It is a chromosomal disorder which occurs due to an error in cell division, leading to an additional copy of chromosome 21. It tends to hamper the physical and cognitive abilities of persons and also makes them susceptible to various health disorders.