There are four different types of genetic disorders: single-gene, multifactorial, chromosomal, and mitochondrial. Single gene, which is also called as Mendelian or monogenic inheritance, is caused by changes or mutations that occur in the DNA sequence of one gene. There are more than 6,000 known single-gene disorders, which occur in about 1 out of every 200 births.

Multifactorial disorder is caused as also called complex or polygenic inheritance. This disorder is caused by a combination of environmental factors and mutations in multiple genes. Examples of multifactorial inheritance include heart disease, high blood pressure, Alzheimer’s disease, arthritis, diabetes, cancer, and obesity.

Chromosomes, distinct structures made up of DNA and protein, are located in the nucleus of each cell. Chromosomal abnormalities in the baby may be inherited from the parent or may occur with no family history. 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 disorders occur when there are mutations in the mitochondrial DNA or the non-chromosomal DNA of the cell. These disorders are maternal in origin as only egg cells contribute mitochondria in a developing embryo. Examples of mitochondrial disease include an eye disease called Leber’s hereditary optic atrophy.