A genetic disorder is caused by an abnormality in the genetic composition (including mutation inside the genes, deletion of a particular gene, chromosomal aberrations, or other similar factors) and is passed down from the parent to the children
There are four different types of genetic disorders -- single gene (Mendelian or Monogenic) disorder, multi-factorial (complex or AKA polygenic) problems, chromosomal abnormalities and mitochondrial disorder. Each type of genetic disorder is explained below:
Single Gene Disorders such as cystic fibrosis, sickle cell anemia and Marfan’s Syndrome occur due to alterations or mutations in the DNA sequence of a single gene (as is indicated in the name of this disorder). Single gene disorders are also referred to as Mendelian inheritance disorders. This disorder may be autosomal dominant (the abnormality occurs when a single genes from only one parent is abnormal), autosomal recessive (the abnormality occurs when a single gene in both the parents is abnormal – a prominent example is that of cystic fibrosis and sickle cell anaemia) or X-linked (the abnormality occurs when a single gene on the X chromosome is abnormal – a prominent example is that of Hemophilia). Single gene disorders usually have greater chances of being passed down genetically.
Multi-factorial or AKA Polygenic such as heart defects, cleft lip or cleft palate, and neural tube defects occur due to a combination of several different factors including the impact of the environment on the genes, thereby triggering mutations in multiple genes.
Chromosomal Abnormalities when changes occur in the chromosomes. Chromosomes are responsible for carrying the exact genetic information but changes and alterations in the chromosome can cause various genetic diseases or disorders. The most commonly occurring chromosomal abnormalities include aneuploidy (Down’s syndrome, Turner’s syndrome), deletion of a part of the chromosome, inversion of a piece of the chromosome and translocation.Mitochondrial mutations occur in the mitochondria. Sometimes, mutations may occur in the non-chromosomal DNA of the mitochondria, which is yet another significant type of genetic disorder.
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