Quratulain Khan & Quratulain Fatima Masood & Ayesha Tariq & Somal Khan & Maryam Tirmizi
DOWN SYNDROME (also called tnsomy 21) is a genetic disorder caused by the abnormal presence of the entire or a part of an extra chromosome 21. The disease is named after John Langdon Down, a British doctor who described it in 1866. Down pointed out the striking similarity of facial features among children with the disease when they were compared with those of Blumenbach's Mongolian race. Hence, the disease is sometimes referred to as “mongolism” and “mongolian idiocy.” The disorder was identified as a chromosome 21 trisomy by Jérôme Lejeune in 1959. The typical patient suffering from Down syndrome has a total of 47 chromosomes in all the somatic cells of his body. Such an abnormality accounts for the impaired growth and development of the child. Down syndrome is the leading genetic cause of mental retardation. Latest statistics report the incidence of Down syndrome to be 1 per 800 live ...