Genetic Disorders

Genes are the basic unit of heredity. They hold the genetic information in the form of DNA which can be translated into useful proteins to carry out life processes. These genes undergo a mutation sometimes, which changes the instructions to formulate the protein, due to which the protein does not work properly. Such disorders are known as genetic disorders.

Some disorders are innate, i.e., present by birth, while others are acquired due to mutations in a particular gene.

The disorders can be categorized into two types, namely Mendelian Disorders, i.e., a disorder in a single gene, and Chromosomal Disorders, i.e., a mutation in the chromosomes, the chromosomes are either missing or duplicated.

Types of Genetic Disorders

Mendelian Disorder

  • These disorders occur due to mutations in a single gene and can be easily detected by pedigree analysis.

  • These disorders can be autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive, and mitochondrial.

The most common Mendelian disorders include:

  • cystic fibrosis (autosomal recessive),

  • hemophilia (sex-linked recessive),

  • albinism (autosomal recessive),

  • sickle cell anemia (autosomal recessive).

Chromosomal Disorder

  • These disorders are caused by any alteration in the number or structure of the chromosomes.

  • Sometimes the whole chromosome is gained or lost.

  • This type of disorder is usually fatal and affects many genes.

Some of the major chromosomal abnormalities are:

  • Down’s syndrome- the addition of a chromosome on chromosome 21,

  • Turner’s syndrome-absence of an X chromosome,

  • Kleinfelter’s syndrome-addition of an X chromosome, etc.

Multifactorial Genetic Inheritance

This is also known as polygenic inheritance. These are caused as a result of environmental factors and gene mutations. Some of the examples of this kind of disorder are:

  • heart disease

  • high blood pressure

  • Alzheimer’s disease

  • obesity

  • diabetes

  • cancer

  • arthritis

Mitochondrial Inheritance

This type of genetic disorder is caused by mutations in the non-nuclear mitochondrial DNA. Each mitochondria has 5 to 10 pieces of DNA. The mitochondrial is inherited from the mother. Some of the diseases caused due to mitochondrial inheritance are:

  • Leber’s Hereditary Optic Atrophy (LHON)

  • Myoclonic epilepsy with ragged red fibres

  • Mitochondrial encephalopathy

  • Lactic acidosis

Genetic Counselling

Genetic counselling is one of the remarkable ways of detecting whether a child to be born will be having a genetic disease, or if the person is going to have a genetic disorder. The genetic counsellors can help a person with the diagnosis and treatment of a particular disorder.

Some of the genetic disorders have been treated by gene therapy. Few of the techniques are under trial and will soon be implemented in medical science to cure genetic disorders.

There are many reasons one should go for a genetic counselling:

  • Family history or a previous child with a genetic disease, heart defects, mental retardation, defect in the neural tube, short height, psychiatric disorders, cancer, etc.

  • A parent with an autosomal dominant disease

  • If the pregnant lady is 35 years or older

  • Mother suffering from any disorder such as depression, alcoholism, diabetes, thyroid, schizophrenia, etc.

For more information on Genetic Disorders, keep visiting BYJU’S Biology website or download BYJU’S app for further reference.

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