Why does increase in age of the mother increases the chance of having an offspring with Down Syndrome?
I want to know the molecular basis of this observation.
Answer There is a lot of chromosomal abnormalities that may cause Down syndrome, but only non-disjunction of sister chromatids is associated with the maternal age. Although the molecular reasons for this observation are not absolutely clear; it is speculated that with the course of the time oocytes suffer from multiple molecular abnormalities: non-separating cohesins, pathologic SAC proteins (spindle assembly checkpoint), malformations in the synaptonemal complex and even epigenetic changes.
Source: Maternal age and chromosomally abnormal pregnancies: what we know and what we wish we knew. Curr Opin Pediatr. 2009 Dec; 21(6): 703–708. doi: 10.1097/MOP.0b013e328332c6ab