Genetic Disorders

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Genetic Disorders

Genetic disorders are classified into Chromosomal. Single-genic, Polygenic and Mitochondrial disorders


Both environmental and genetic factors have roles in the development of any disease. However there are several genetic disorders caused exclusively by anomalies in the genetic material of an individual.


Genetic disorders are classified into the following:
1. Chromosomal Disorders- Chromosomes, which are distinct structures made up of DNA and protein, are located in the nucleus of each cell. Abnormalities in the chromosome structure or number results in a disease. Several chromosomal abnormalities can be detected by microscopic examination. Down syndrome or trisomy 21, a classical example, is a common disorder that occurs due do the presence of three copies of chromosome 21.

2. Single-gene disorders - Also called Mendelian or monogenic disorders. Mutations that occur in the DNA sequence of a single gene give rise to these disorders. They occur in about 1 out of every 200 births, and have a specific pattern of inheritance such as autosomal dominant, autosomal recessive and X-linked. There are more than 6,000 known single-gene disorders and some of the famed examples are cystic fibrosis, Huntington’s disease, Marfan syndrome and sickle cell anemia.

3. Multifactorial or polygenic Disorders - These disorders are caused by a combination of mutational changes on an array of genes and environmental factors.. Its complexity makes it more difficult to analyze multifactorial disorders. Examples include cancer, diabetes, heart disease, obesity, high blood pressure, Alzheimer’s disease and arthritis. Several mutational changes in the BRCA genes that increase the risk of developing breast cancer have been discovered.

4. Mitochondrial Disorder - These rare type of genetic disorders arise from changes in the DNA of mitochondria which are organelles found in the cytoplasm of plant and animal cells, responsible for cellular respiration. Each mitochondrion may contain 5 - 10 circular pieces of DNA and are usually passed on from the mother to the offspring.

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One of my relative's son has low biotinidise enzyme. He was born 2 weeks ago in USA and is using biotin 5MG tablets now. They are in USA and want to come to Chennai - in 3 months from now [2-June-2015]. They were told that a blood sample needs to be tested for biotin every 6 months to adjust the dosage of Biotin prescribed for the baby. Is Biotin tablets for infants available in Chennai? Is there medical centers/labs/doctors at Chennai who treats such biotin related gene disorder? Any early response is greatly appreciated. Thanks !

mjav123

Dear Doctor, My daughter is suffering from CAH and she need a genital corrective surgery. She is under AIIMS treatment. I do not know if where CAH is being treated. Due to a long waiting time I wish to have an alternate opinion. Please suggest me. Thanks a lot.

Hello Doctor, can you please suggest the best place in India for genetic counseling. My daughter who is now 5 1/5 years old had long segment hirschsprungs diseases at birth which was treated with pull through surgery. Both me and my husband are not aware of any family history of hirschsprungs in our family. Now I am planning for another kid but before that want to be sure of the underlying reason for my daughter's condition and the chances of recurrence in future pregnancies. Any advice on this will be very much appreciated. Thank you!

The best genetic counselor in India by popular consensus is Dr.Ashok Prasad who is a professor also holding a genetic counseling masters from Brandeis University. He works only on a charitable basis in Gorakhpur but am sure could be persuaded to advise you

tulika12345

Hello doctor, we had a child who was effected by spinal muscullar attrophy[type one]. Now we are planning for our next baby. doctor told us to go for CVS testing. but I want to know whether there is any other ideal option for us.Pleas give me suggestions. Subhajit bhowmick

helllo doctor,my wife is a pregnant our doctor is prefre to amniocentesis so plz tell me where i do in delhi,india and how much it cost

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