Evolution

This photo is of a double transgenic mouse embryo at 18.5 days old, seen here at 17x magnification. Mice are a great model for studying mammalian gene function and protein regulation (one reason being due to our similarity). Transgenic mice have additional DNA inserted artificially. They are particularly useful in modelling human diseases caused by overexpression or misexpression of a protein.

Ge

nerally foreign DNA results in a gain for the mouse (such as the production of a new protein) but it can disturb or interrupt how an existing gene is expressed. In either case, the consequence can often by seen in the mouse's phenotype (the physical manifestation of genes, such as appearance, tissues and behaviour). Knockout mice are a common type of transgenic mouse, taking their name from where a gene has been "knocked out" or inactivated.

Photo credit: Gloria Kwon. Taken using Brightfield, Darkfield, Fluorescence (GFP and RFP).

http://www.nikonsmallworld.com/galleries/entry/2007-photomicrography-competition/1

For more on transgenic mice: http://genome.wellcome.ac.uk/doc_wtd021044.html

For more on knockout mice: http://www.genome.gov/12514551