Artwork of a four-cell embryo

Under development

Controlled cell division is a key part of development

Perhaps the most remarkable fact in biology is that the several tens of trillions (1 trillion = 1012, or 1,000,000,000,000) of cells that make you develop from a single cell – a fertilised ovum, or zygote. Controlled cell division is crucial for development.

In the early stages of embryogenesis, the zygote undergoes cellular division to create two cells, which then go on to make four cells, and then eight (and so on). Each division takes between 12 and 24 hours, so the eight-cell stage is usually reached at around day 3. Once the embryo has between 16 and 32 cells, the dividing cells can begin to differentiate and form structures that fold, get reshaped or even migrate to different locations. Disrupting just one of the many genes involved in controlling all these subtle shifts increases the risk of developmental defects. The effects of these defects may be felt much later on in adult life, not just at birth.

Lead image:

Artwork of a four-cell embryo.

Miles Kelly Art Library/Wellcome Images

Further reading

About this resource

This resource was first published in ‘The Cell’ in February 2011 and reviewed and updated in September 2015.

Cell biology, Medicine, Health, infection and disease
The Cell
Education levels:
16–19, Continuing professional development