Several studies have associated non-disjunction with increased maternal age. This is called trisomy 21 and accounts for 95% of Down syndrome cases. When fertilization between the male and female reproductive cells takes place, the baby cells thus have 3 copies of chromosome 21 with a total number of 47 chromosomes. During the process of formation of these cells, if the separation of the pair of chromosome 21 does not happen properly, the reproductive cell could have an extra chromosome 21. The cells of the human body have 23 pairs of chromosomes (46 chromosomes), while the reproductive cells, that is the egg and the sperm each have only one set of chromosomes i.e. The improper separation of chromosome 21 ( non-disjunction).What are the Causes and Types of Down Syndrome?ĭown syndrome has a genetic basis, where the cells of the affected person have an extra chromosome 21. Couples who already have a Down syndrome child have increased chances of recurrence compared to the general population.It has been widely reported that Down syndrome children are more commonly born to older mothers - but in a country like India too, where women get married and produce children at an early age, this condition is equally prevalent as anywhere else in the world.With the help of advances in medicine and the rise in community support groups, 80% of Down syndrome patients reach their 50 th birthday and beyond.Congenital heart diseases appear in around 40% of Down syndrome individuals contributing to the increased number of their deaths in infancy.Hearing deficits occur in 60 - 80% of children with Down syndrome.Yearly, 3000 to 5000 children are born with this syndrome worldwide.
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