Genetic Diseases

Problems In Our Genetic Building Blocks


Genetic diseases arise due the abnormalities in DNA. These abnormalities may occur in wide variety, from a single mutation in a single gene, to duplication of a whole chromosome or deletion of a chromosome.


On a  large scale, genetic  abnormalities can be classified as single gene defects, multifactorial disorders, chromosomal abnormalities and mitochondrial disorders. Single gene defects are mutations that occur in the  DNA sequence of a single gene. There are more than 6000 single gene disorders known, with a prevelancy of 1 in every 200 births. Cystic fibrosis, Sickle-cell Anaemia, Marfan Syndrome are examples of such disorders.


Multifactorial disorders can be identified as defects in multiple genes as a result of mutations and  environmental factors. For example; breast cancer is related to the genes on chromosome 6, 11, 13, 14, 15, 17, 22. Most of the common diseases (heart diseases, diseases concerning blood pressure, Alzheimer, arthritis, diabetes and cancer) are multifactorial. Multifactorial disorders are inherited  just like the eye color, skin color or fingerprint of an individial.


Chromosomal abnormalities can be defined as quantitative and structural alterations in  the chromosomes that are tightly packed and preserved  inside the cell. For example; Down Syndrome is caused by a defect on chromosome 21, Turner Syndrome occurs as a result of a defect on chromosome 45, Klinefelter Syndrome arises as a result of a defect on chromosome 47.

Mitochondrial disorders are the results of mutations in the mitocondrial DNA. Dementia and epilepsy are results of such defects.


Genetic tests are the tests used to diagnose genetic abnormalities; they detect the presence of a specific mutation, chromosomal defect or a major protein in the gene level, molecular or biochemical level, and provide the clinicians data and guidance. The test material neccessary for genetic tests can be obtained from various sources such as the blood, body fluid or biopsy specimen of the individual.

Real-Time PCR due to its advantages of diagnostic accuracy, speed and effectiveness, is more widely used and preferred to other genetic tests.