Genetic disorders are caused by the mutations or abnormalities that occur in a chromosome or genome. These abnormalities may appear phenotypically at any time of a human life. It is being estimated that there are around 4,000 genetic disorders which affect the human life. But this number keeps changing as we know more about our gene and genome. Types of mutations like single nucleotide mutation, chromosomal aberration, mitochondrial genome and also environmental factors play a role in inducing these genetic disorders in humans.
Single Gene Disorder:
When mutations or change in DNA sequence of a single gene leads to a disorder, then this condition is known as single gene disorder. The changes in the gene will lead to the formation of non-functional proteins in the body. This non-functional protein will lead to a disorder or genetic condition. For example Cystic fibrosis is an example for single gene disorder. Cystic fibrosis condition is caused by a mutation in chromosome 7 gene known as cystic fibrosis transmembrane conductance regulator (CFTR). The mutation in the gene CFTR produces the abnormal non-functional protein, which affect the movement of sodium chloride in the body cell. This leads to the formation of abnormal thick mucus in the lungs. This in turn makes it difficult for patients to breathe and digest. This is also an example for recessive genetic disorder. Recessive genetic disorders are the one when both the alleles of a gene are defective then only the condition occur phynotypically. That is both the parents should pass the defective gene to their offspring then only this condition appears in once life.
Dominant genetic disorders are the one where only one allele of the gene is replaced by the defective code. Example for this condition is Marfan syndrome.
Mitochondrial Genetic Disorder:
Mitochondrial genetic disorder occurs due to the genetic mutations that occur within the mitochondrial DNA. Leber Optic Atrophy is an example for mitochondrial genetic disorder. In this condition optical nerve cells are degenerated in the body.
When small portion or entire chromosome are duplicated, altered or some portion of chromosome is missing then a condition known as chromosomal genetic disorder occur. Dpwn's syndrome is an example for this condition. This condition occurs as a result of trisomy of chromosome 21. that is an extra copy of chromosome 21 leads to the condition known as Down's syndrome. This extra copy of DNA will lead to more production of proteins, this in turn will disturb the normal functions of the body.
Multifactorial Genetic Disorder:
Multifactorial genetic disorders are caused by combination of many factors like gene mutation, small variations in the chromosome structure and also environmental factors. Cancer, heart conditions or disease are best examples for this type of genetic disorder.
A single mutation in the gene will not induce skin cancer. Rather multiple DNA mutations caused by environmental factors like X-ray or UV rays may increase the chances of developing skin cancer. This type of genetic disorders is very difficult to diagnose, treat.
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