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Sankara Nethralaya
Sankara Nethralaya
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Department of Genetics and Molecular Biology

Genetic diseases:

A genetic disease or disorder is an abnormality in an individual's genetic material (genome). The abnormality could be a change in an individual’s DNA (mutation) or chromosomes (aberration)

Genetic diseases can be inherited or transmitted to next generation if the mutations are in the germ cells of the body (the cells involved in passing genetic information from parents to offspring). However, genetic diseases can also result from changes in DNA in somatic cells.

Genetic disorders can be categorized as (A) single-gene, (B) multifactorial, (C) chromosomal, and (D) mitochondrial.

(A) Single-gene (also called monogenic or Mendelian) disorder: This type is caused by changes or mutations that occur in the DNA sequence of one gene. A Gene is a functional unit of the genome consisting of a sequence of DNA that occupies a specific location on chromosome and code for proteins. When a gene is mutated so that its protein product can no longer perform its normal function, a disorder can result. Single-gene disorders are inherited in recognizable patterns: autosomal dominant, autosomal recessive, and X-linked.

(B) Multifactorial (also called polygenic or complex): This type is caused by a combination of environmental factors and mutations in multiple genes.

(C) Chromosomal: Chromosomes, discrete structures made up of DNA and protein, are carriers of genetic material. Abnormalities in chromosome structure as missing or extra copies or gross breaks and rejoining (translocations) can result in disease.

(D) Mitochondrial: This relatively rare type of genetic disorder is caused by mutations in the non-chromosomal DNA of mitochondria. Mitochondria are small round or rod-like organelles involved in cellular respiration and found in the cytoplasm of plant and animal cells. Each mitochondrion may have 5 to 10 circular pieces of DNA.

Chromosomal analysis:
Chromosomal analysis / Cytogenetics involve the study of human chromosomes in health and disease. The chromosomes are visualized after staining, in light microscopy as they display a characteristic dark and light banding pattern according to the DNA content that is unique for individual chromosome. It serves as an important laboratory diagnostic procedure in the field of prenatal diagnosis, in patients/families with history of mental retardation, multiple birth defects, abnormal sexual development, infertility or multiple miscarriages. The field also finds its application in malignancies and hematological disorders.

Normal Female karyotype
Normal Male karyotype

Molecular diagnostics:

Molecular diagnostics assess your biological makeup at the genetic level. Sequencing the DNA can reveal variations between individuals which may represent a predisposition to develop a disease. Intricate pathogenesis pattern of a genetic disease can be addressed through molecular diagnostics.

Molecular diagnostics is the accurate method to screen the patients with ophthalmic genetic disorders.
It provides more information about the disease paving way for tailored treatments and personalized genomic medicine.
It can provide better disease management through genetic counseling.
Molecular diagnostics also helps patients to participate in treatment / clinical trials (research studies in people).

Genetic counseling:

Genetic counseling is a service which elucidates the patients on genetic diseases. It is an understanding of facts behind the science of genetics. It is a cognitive operation of recuperating the quality of life. Our department dispenses this service for people with ocular diseases due to genetic defects.