Chromosomal Disorder in Human - Part 1

Briefly about the chromosomal disorders or disorders found in humans and their types, we have known the Mendelian Disorder Occur in Human Beings found in the human species. In this article, we will learn about the disorder or abnormality caused by deficiency or excess in the number of chromosomes in humans.

Important Facts Related to Tricolor

Chromosomal Disorder in Human

Many changes and malformations are seen in the human body due to changes in human chromosomes. Changes in chromosomes are mainly of two types – first, changes in somatic chromosomes and second, changes in sex chromosomes. If we talk about Why and when do these changes happen? So these changes mainly happen at the time of gametogenesis or at the time of fertilization, apart from this it can also happen under certain circumstances like radiation etc.

Types of Chromosomal Disorder

As we mentioned in our previous article Mendelian Disorder Occur in Human Beings, there are two types of chromosomal disorders –

1. Aneuploidy or Heteroploidy
   1. Autosomal Aneuploidy 
      1. Down’s Syndrome or Mangolism
      2. Edward’s Syndrome
      3. Patau’s Syndrome
   2. Aneuploidy Involving Sex Chromosome
      1. Turner Syndrome
      2. Klinefelter’s Syndrome
      3. Super Female
      4. Super Male
2. Euploidy or Polyploidy

Green Hydrogen : A Source of Renewable Energy

1. Aneuploidy or Heteroploidy

When there is a change in the number of chromosomes in a particular pair of chromosomes, it is called aneuploidy.  If this change is followed by an increase in the total number of chromosomes by one or more chromosomes, then it is called hyperploidy.  whereas if the number is decreased by one or more, it is called Hypoploidy.

Many symptoms appear together in the human body through both forms of Aneuploidy, Hyperploidy or Hypoploidy, and taking the form of disease, which is called Chromosomal Syndrome. These syndromes mainly arise due to non-separation of homologous chromosomes at the time of incomplete meiosis in gametogenesis. 

There are different stages of aneuploidy, which are as follows –

Various Stages of Aneuploidy

1. Monosomic
2. Nullisomic
3. Polysomic

1. Monosomic

When there is only one chromosome in a particular pair of chromosomes, while all other pairs have two chromosomes, then this condition is called monosomy or monosomy. This condition is represented by (2n – 1).

2. Nullisomic

When both chromosomes of a particular pair are absent and all other chromosomes have two chromosomes, then this condition is called diplosomal. This state is denoted by (2n – 2).

3. Polysomic

When the number of chromosomes in a particular pair of chromosomes is more than two and all other pairs have two chromosomes, then this condition is called polysomic. There are many types of this. Like – three chromosome or trisomy (Trisomic – 2n + 1), four chromosome or tetrasomy (Tetrasomic – 2n + 2), five chromosome or pentasomy (Pentasomic – 2n + 3) etc.

Ocean Current Stream & its Origin

Types of Aneuploidy

Anuploidy is of Two Types –

A. Autosomal Aneuploidy

These anaploidy are found in the somatic chromosomes (in any one of the 22 pairs of chromosomes). These are of the following types –

i . Down’s Syndrome or Mangolism

• This syndrome was first described by Langdon Down, after whom it was called Down's syndrome.
• Due to the face of the people suffering from this disease being similar to the Mongols, it is also called Mongolian Idiocy.
• In Down's syndrome, there are 3 chromosomes instead of 2 in the autosomes of 21 pairs of chromosomes, which shows a trisomy condition, that is, the total number of chromosomes in the body becomes 47.
• Such persons have slanting eyes, broad forehead, short and broad neck, thick tongue, underdeveloped brain, short stature, small ears and round nose, protruding lower lip and irregular palms and feet.
• Such persons are more likely to suffer from hernia, diabetes, leukemia and infectious diseases.
• The age of these persons ranges from 12 to 14 years.

ii . Edward’s Syndrome

• This disease was studied by J.H. Edward, due to which it was called Edward's syndrome.
• In this, there are 3 chromosomes in place of 2 in the autosomes of the 18th pair of chromosome, which shows a trisomy condition, that is, the total number of chromosomes in the body becomes 47.
• The brain of such children is underdeveloped and there are disorders in the organ system of the body such as ear deformity, heart defect and disability.
• Children suffering from these diseases survive only from 6 months to one year.

Twins Children

iii . Patau’s Syndrome

• This disease was studied by K. Patau, due to which it was called Patau syndrome.
• In this, there are 3 chromosomes in place of 2 in the autosomes of the 13th pair of chromosome, which shows a trisomy condition, that is, the total number of chromosomes in the body becomes 47.
• The brain of such children is rudimentary, the upper lip is cut from the middle, deafness, there is a crack in the palate. Apart from this, there are deformities in their organs and organ systems.
• The age of these children is up to three months.

We will discuss remain other Mendelian disorder in next article under heading Chromosomal Disorder in Human - Part 2 . Click here to read it.

Murals at theVeerata Chakra of the National War Memorial