Dr Marnie Blewitt wants to know how a human being is made: how does a single fertilised egg develop into an adult with millions of cells performing a myriad of different functions.

“How does a cell know which of its 30,000 or so genes should be active and which should be dormant?” says Marnie, a researcher at the Walter and Eliza Hall Institute of Medical Research.

The key, she says, is in the punctuation—the genome is labelled with tags and flags to indicate which genes are active and which are not. This ‘epigenetic’ information seems to be what guides the cell to turn genes on and off.

Marnie is using the X chromosome to try to understand epigenetics. The X chromosome is unusual because in males there is only one copy of this chromosome, while in females there are two copies. One of these copies has to be turned off for normal development.

“The second copy of the X chromosome has to be completely inactivated. We know it is packaged away and silenced through a number of steps during development from a fertilised egg into an adult. I’m using it as a model system to help unravel the complex story of epigenetic control,” says Marnie.

In August 2009 Marnie received one of three L’Oréal Australia For Women in Science Fellowships.

Further information: Marnie Blewitt, blewitt@wehi.edu.au, www.scienceinpublic.com.au/loreal