Publisher's Synopsis
Down syndrome (DS) is a most common human congenital anomaly with several physical and mental traits, caused by an extra chromosome present on 21st chromosome, also known as trisomy 21. Trisomy 21 is caused by abnormal segregation during meiosis with around 90% cases of mothers with the incidence of 1 in 800 live births. There is an increased tendency of miscarriage with trisomic fetuses, thus the DS patients develop various medical conditions. In developed countries the life expectancy of the DS has increased up to 55 years with advances in medical treatment. An extra maternal chromosome involves predominantly 90% of trisomic conditions, mainly due to meiotic errors in the egg. In humans the frequent cause of fetal death is due to the chromosomal abnormality. Within the initial 15 weeks of gestation period, half of the spontaneous abortions are chromosomally aneuploid, and approximately 50% of trisomies occurs due to spontaneous abortions.
