Chromosomal Disorder in Human - Part 2

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.

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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

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B . Aneuploidy Involving Sex Chromosome

This aneuploidy is found in the sex chromosome (23rd pair chromosome), especially in the X chromosome. It has the following types –

i . Turner Syndrome

• It was studied by Turner, due to which it was called Turner syndrome.
• In such individuals, only one chromosome (X) is present in the sex chromosome, while the other sex chromosome is absent. Thus, it forms a monosomic condition. Therefore, the total number of chromosomes in the body is one less i.e. 45 chromosomes (44 + X).
• It is due to disjunction of chromosomes during oogenesis or spermatogenesis.
• Their body is rudimentary, chest flattened, short in stature, female-like, barren or barren. Complete development of genitals is not possible.
• In childhood, she remains a normal girl, but in adolescence, the ovary remains undeveloped, due to which she becomes eunuch or impotent.

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ii . Klinefelter’s Syndrome

• This was studied by Klinefelter, due to which it was called Klinefelter's syndrome.
• Such individuals have 3 chromosomes (XXY) instead of 2 in the sex chromosome. This is a trisomy condition. Therefore, the total number of chromosomes in the body is 47 chromosomes (44 + XXY).
• These syndromes result from the fertilization of normal sperm (Y) and abnormal egg (XX) or abnormal sperm (XY) and normal egg (X).
• They have characteristics of both men and women.
• Due to Y-chromosome, their body is long and like that of normal men, while due to X-chromosome, testes and other genitals and reproductive glands remain rudimentary. Sperms are not formed in them and these males are sterile. This condition is called hypogonadism.
• Their face is like that of women and there is less hair on the body. In these, breasts like women develop, this condition is called gynecomastia.
• Super male and super female are also a form of Klinefelter's syndrome.

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iii . Super Female

• The number of X-chromosome increases in the sex chromosome of such females.
• The number of chromosomes in such women is 47 ( XXX ) , 48 ( XXXX ) or 49 ( XXXXX ) .
• These women are fertile, but by nature they are intelligent.

iv . Super Male

• Such males have an excess of Y-chromosome in the sex chromosome.
• They have XYY chromosomes in their sex chromosomes.
• These men are tall, dull-witted, angry, sensual and criminal in nature.

2. Euploidy or Polyploidy

• In this, the increase in the number of chromosomes is in multiples of the total number of haploid chromosomes (n = 23). For example, triplet (3n) means 3 x 23 = 69, quadrupled (4n) means 4 x 23 = 92, pentaploidy (5n). That is, 5 x 23 = 115 and so on.
• The jaw of such persons is small, fingers and toes are joined and the brain is underdeveloped.
• The main reason for polyploidy is the absence of meiotic division. Apart from this, even if an egg is fertilized by two sperms, a triploid state is formed.

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Other Chromosomal Disorder

As we mentioned in our previous article  Mendelian Disorder Occur in Human Beings , other chromosomal disorders include deletion of an arm of a chromosome, shortening of an arm, or lengthening of an arm. While there is no change in chromosome number. 

Following are some examples of this –

1. Cri – du – chat Syndrome or  Cat's meow syndrome.
2. Myelogenous Leukemia

1. Cri – du – chat Syndrome Or  Cat's meow syndrome.

• This syndrome was studied by J. Lejeune.
• In this, there is a deletion of the short arm of the 5th pair of the somatic chromosome.
• In childhood, these children make sounds like a cat while crying, due to which it is called Cree-doo-chat syndrome or cat's meow syndrome.
• In this, the total number of chromosomes in the body remains only 46.
• The eyes of these children tend to slide to the sides, due to which the distance between the eyes increases.
• Physical and mental deformities are found in these children.

2. Myelogenous Leukemia

• This condition is caused by a deletion of the 22nd pair of chromosome or an arm of the Philadelphia chromosome.
• In this, the total number of chromosomes in the body remains only 46.
• Due to this, there is a fatal disease called Blood Cancer.

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