Melanie Zhi Qing Lim

Project Title: Spatial regulation of recombination during meiosis

DNA molecules are the cell’s “instruction manual” – they provide cells with information to carry out their function. Each DNA molecule is organised into structures called chromosomes. Nearly all cells in our body contain 46 chromosomes or 23 chromosomes pairs as we inherit one set each from our mother and father. Therefore, reproductive cells (egg and sperm) have to undergo a specialised cell division known as meiosis. At the end of meiosis, their chromosome numbers are halved.

Meiosis involves several distinct stages, however, one critical event is called “crossing over”. During crossovers, the maternal and paternal chromosomes pair up and exchange sections of their DNA between each other by breaking and repairing the DNA (known as recombination). This event is crucial for accurate chromosome segregation during meiosis. Should errors occur, this would result in reproductive cells having an abnormal chromosome count, a feature known as aneuploidy. Aneuploid egg or sperm that participates in fertilization can lead to miscarriages or birth defects like Down’s syndrome.

Importantly, these crossovers during meiosis do not occur randomly along chromosomes. In my project, I want to establish how crossovers are positioned on chromosomes. Findings from this work will enable better understanding of the causes of pregnancy loss and congenital diseases involving abnormal chromosome numbers.