Answer to Question #65438 in Genetics for Sanjukta Ghosh

Question

This could fall under Molecular biology too.

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 1

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