siliconindia | | June 20189genome's contribution to health and disease. Genetic analyses have be-come essential in clinical practice and research. Although, many of the cures for genetic conditions are yet to materialize, the secrets of dis-eases are indeed being revealed, in ways that will transform medicine over coming years.Approximately 10 years ago, karyotyping was the gold standard in patients with dysmorphism and intellectual disability or any other congenital anomalies. However, a latest high-throughput technology, chromosomal microarray that en-ables us to analyse the chromosomes at a greater depth, 100 times as com-pared to conventional karyotype has become the first line diagnostic test replacing karyotyping. Next-genera-tion sequencing (NGS) which allows sequencing of multiple genes at the same time has dramatically acceler-ated the pace of biological research and diagnosis. These advancements have greatly increased the diagnos-tic value of several, previously un-known/undiagnosed disorders. Over 7000 distinct genetic disorders are already defined and more are being discovered at an increasing pace. Most well-known genetic con-ditions are Down syndrome and -thalassemia. The incidence rate of these conditions still remain aston-ishingly high with Down syndrome amounting up to 1:800 live births and -thalassemia up to 10,000 live births per year. Every pregnant woman is at the risk of having a child with Down syndrome and they can be screened by offering a sim-ple blood test known as Double test, which is a screening test for Down's syndrome between 10 and 14 weeks of pregnancy. The screening tests along with Nuchal translucency scan will identify about nine out of 10 Down's syndrome pregnancies. But it does not detect all pregnancies with Down's syndrome. If wom-en are found to be in the high-risk group then a diagnostic test will be offered after counselling. As it is in-vasive test, there is small chance of miscarriage. Currently, safer test op-tion is also available, non-invasive prenatal screening (NIPS). It will be able to detect small fragments of DNA from the baby floating in the mother's blood, called cell-free DNA (cfDNA). The cfDNA test per-formed significantly better than the current screening test for Down's syndrome with 99 percent accura-cy. If this test comes in the high-risk group then the result should be con-firmed with the needle test.-thalassemia is a blood disor-der in which abnormal production of haemoglobin occurs and patients require frequent blood transfusion throughout their lives. India has a huge burden of this disease with 3-4 percent population being carriers; usually carrier individuals will not be affected themselves but they can be at 25 percent risk of having baby with -thalassemia. The carriers can be identified by performing simple Hb-electrophoresis testing. It is im-portant to identify the defect at the gene level before prenatal diagnosis, identifying whether fetus is affected at 12-13 weeks of gestation. With the help of pre-implantation genetic diagnosis/screening, PGD/PGS which is IVF+ genetic study, we can screen for known genetic disease in the family and chromo-somal abnormality in the embryo. In this, embryo biopsy is taken on day five and cells are then screened and then good embryo is transferred in the womb. This helps in prevention of genetic disease and increase in the IVF success rate also.Presently many multifactorial complex genetic conditions are of high concern among the population that includes autism and cancer. Autism is a complex neurodevel-opmental disorder characterized by impaired social interaction, restricted and repetitive behavior. The exact cause of autism is still being investigated. Research into causes suggests that a combination of factors - genetic & environmen-tal - may account for differences in Dr. Mitesh Shetty
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