Chromosomal Abnormalities: Causes, Symptoms & Treatment

Chromosomal abnormalities occur when there are changes in the number or structure of chromosomes, leading to genetic disorders. These abnormalities can result from errors during cell division, such as non-disjunction or structural changes like deletions or duplications. Conditions like Down syndrome, Turner syndrome, and Klinefelter syndrome are caused by chromosomal abnormalities, In this article, chromosomal abnormalities, structure and function of chromosomes, types of chromosomes, types of chromosomal abnormalities, causes of chromosomal abnormalities, diagnosis of chromosomal abnormalities are discussed. Chromosomal Abnormalities is a topic of the chapter Principles of Inheritance and Variation in Biology.

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This Story also Contains

1. What are Chromosomal Abnormalities?
2. Structure and Function of Chromosomes
3. Types of Chromosomes
4. Types of Chromosomal Abnormalities
5. Causes of Chromosomal Abnormalities

What are Chromosomal Abnormalities?

The chromosomal abnormalities are the ones where there is a change in the normal number or pattern of the chromosome structure. The genetic disorder varies in its cause and development. It might have been developed due to an error in the cell division, which significantly changed the structure of chromosomes. Those abnormalities can make a big difference in the life and other attributes of a person: growth, development, and overall health.

Most of the chromosomal abnormalities are associated with the health problems of physical malformations, intellectual disabilities, and susceptibility to some diseases. A common chromosomal abnormality is Down syndrome, which results from the presence of an extra copy of chromosome 21 and leads to developmental delays. Knowing these abnormalities is very important so that early diagnosis is done, and management is done appropriately to better the quality of life of these individuals.

Structure and Function of Chromosomes

Chromosomes are DNA and histone entities that are found in the long threads residing in the cell nucleus of a plant. These threads are associated with heredity, and it is important to ensure that genetically inherited material is transferred from one generation to the next without deterioration. They are important for the division, growth, and well-being of a cell and carry all the information needed for the construction and maintenance of an organism.

Chromosomes are, by and large, pretty complex structures, as they consist of a couple of important parts, listed below:

• Chromatid: A chromosome consists of two identical sister chromatids sticking to each other at the region known as the centromere.

• Centromere: This is the mid-point of the chromosome where the two sister chromatids are attached. It plays a very important role in cell division, as the centromere is responsible for the proper division of chromosomes into daughter cells.

• Telomere: End of the chromosome that acts as a cap to the chromosome. Telomeres give protection to the ends of chromosomes against degradation and against sticking to each other.

Also Read:

• MCQ Practice on Chromosomal Abnormalities
• Principles of Inheritance and Variation
• Genetics
• Molecular Basis of Inheritance

Types of Chromosomes

Based on functions and genetic contents, chromosomes are divided into two types, they are:

• Autosomes: These are the chromosomes that are not directly involved in determining the sex of an individual. In a human being, there are 22 pairs of autosomes.

• Sex Chromosomes: They are known to determine the sex of an individual. In humans, the two chromosomes are expressed as XX for females and XY for males.

Types of Chromosomal Abnormalities

The chromosomal abnormalities are categorised as:

Numerical Abnormalities

It is an abnormality caused due to a change in the number of chromosomes. The two most important numerical abnormalities are:

• Aneuploidy: It is a condition where the number of chromosomes in a cell is not a multiple of the haploid set.

• Trisomy: An extra chromosome is present. E.g. Down's Syndrome (Trisomy 21).

• Monosomy: A chromosome is missing. E.g. Turner's Syndrome (Monosomy X).

Structural Abnormalities

Structural abnormalities are caused by an actual change in a chromosome's structure. These types fall into the categories of the following:

• Deletions: A piece of the chromosome is deleted. E.g. Cri du Chat Syndrome.

• Duplications: A piece of the chromosome is duplicated, hence there is an excess of genetic material.

• Inversions: a segment of a chromosome attaches to the same chromosome where it originated but in the reverse order.

• Translocations: a segment is taken out from one chromosome and inserted into a different chromosome. Example: Chronic Myelogenous Leukemia.

Causes of Chromosomal Abnormalities

Chromosomal abnormalities are caused by various factors:

Errors in Cell Division

• Nondisjunction: Chromosomes do not perfectly separate from each other during cell division, creating an irregular number of chromosomes.

• Errors in Meiosis and Mitosis: During meiosis, errors can be of consequence in gametes and cause a chromosomal abnormality; in the case of mitosis, it is with somatic cells.

Environmental Factors

• Radiation: High doses of radiation can damage the chromosomes and cause an abnormality.

• Chemicals: Some also have been believed to damage the human chromosome; these include chemicals found in tobacco smoke and other pollutants.

• Viruses: Infections from some viruses can interfere with chromosome structure and function.

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