Genetic Disorders: Definition, Cause, Symptoms, and Examples

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What are Genetic Disorders?

Genetic disorders are type of biological inheritance which follows the principles that have been proposed by Gregor Mendel in the year 1865 and 1866.

Generally, in humans the Genetic disorders are type of genetic cause which happens due to abnormalities or defects in the genome of an individual.

These disorders are seen in an affected individual from birth and can be diagnosed and can be treatment to reduce the impact even though it cannot be cured purely.

It can also be identified the passages of traits by pedigree analysis or family tree.

This type of genetic disorders is rare, affecting one of thousand individuals.

These disorders may or may not be inherited. Inherited disorders are the ones which are passed through germ line cells, where as in non-inheritable conditions these disorders are caused due to mutations or some changes in the genetic material.

A best example for this condition is cancer, which is either caused by environmental conditions or lifestyle factors or though inherited conditions.

Principles of Genetic Disorders

The research carried out by Mendel on pea plants stands as a base for understanding all the inheritances which are characterized by a single gene disorders.

Mendelian genetic disorders are caused due to a mutation in a single gene locus, where the locus is present in autosome or allosome.

It occurs either as a dominant or a recessive allele. If the individual who is having this disorder then the pedigree analysis is followed to find whether this disorder is present in an autosome or allosome in large families then dominant and recessive condition can also be found through that.

Mendel also suggested two laws for knowing the inherited disorders better.

Law of Segregation

Mendel’s law of segregation states that at the time of formation of genes two genes are separated so that each gene will carry one of the alleles.

Law of Independence

Mendel’s law of independence states that during the time of separation of gametes, each gene pair separates independently with other pairs.

It can also be said that the allele received by the gamete for one pair is independent of the allele received for the other allele.

Types of Genetic Disorders

Genetic disorders are classified depending upon the Mendel’s law of inheritance.

It is of five types namely;

 Autosomal dominant

 Autosomal recessive

 Sex-linked dominant

 Sex-linked recessive

 Mitochondrial

All these types of Mendelian disorders can be identified with the help of pedigree analysis.

Examples of Genetic Disorders

Examples of Mendelian Genetic disorders include;

 Sickle cell anaemia

 Muscular dystrophy

 Cystic fibrosis

 Thalassemia

 Phenylketonuria

 Colour blindness

 Skeletal dysplasia

 Haemophilia


It is one of the types of sex-linked recessive disorder. Here, the unaffected carrier mother passes this condition to their sons.

This disorder is rare in females because they get only one gene through the parents at most of the times, so the probability will be as a carrier mother or as an unaffected one.

So, it is very rare that females will be an affected individual.

In this disorder the blood will not clot easily after an injury or any other accidents.

Males are most frequently affected to this type of disorder.

Sickle Cell Anaemia

It is one type of autosomal recessive disorder where the disorder is carried to the offspring’s if two parents are carriers of this disease.

This disorder is caused due to the mutation in the hemoglobin molecule where the glutamic acid present in the sixth position in a hemoglobin molecule in a beta chain is replaced by valine.

So, the hemoglobin molecules acquire a change in shape, by converting into a sickle shape from its normal biconcave shape which reduces the oxygen carrying capacity of the cells and this shape of molecules cannot be easily passed through the vascular system and it results in forming a block in small blood vessels such as capillaries.


It is one of the autosomal recessive disorder caused due to the inborn error of phenylalanine metabolism which is one of the important amino acid needed for the body.

This disorder, affects the conversion of enzyme phenyl alanine into tyrosine as a result phenylalanine is being accumulated in the body which results in formation of many derivatives and causes mental retardation in most of the cases.


It is one of the types of autosomal recessive disorder. In this type of disorder body makes abnormal amount of hemoglobin so it leads to a condition where higher amount of red blood cells is destroyed and causes anemia.

It causes symptoms such as abdominal swelling, dark urine excretion, deformities of facial bones etc.

Cystic Fibrosis

It is one of the types of autosomal recessive disorder where the lungs and digestive system gets affected completely and there is also a thick production or secretion of mucus which blocks the lungs and pancreas.

Usually, the person affected with this syndrome has very short life span.

Genetic Disorders Citations


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