I've written about this fascinating _Drosophila_ gene, _bicoid_, several times before. It's a [maternal effect gene](http://pharyngula.org/index/weblog/comments/maternal_effect_genes/), a gene that is produced by the mother and packaged into her eggs to drive important early events in development, in this case, establishing polarity, or which end of the egg is anterior (_bicoid_ specifies which end of the egg will form the fly's head). _Bicoid_ is also a [transcription factor](http://pharyngula.org/index/weblog/comments/transcription_factors_and_morphogens/), or gene that regulates the activity of other genes. We also see [evidence that it is a relatively new gene](http://pharyngula.org/index/weblog/comments/bicoid_nanos_and_bricolage/), one that is taking over a morphogenetic function that may have been carried out by several other more primitive genes in the ancestral insect.
**Continue reading** ["Bicoid evolution" (on Pharyngula)](http://pharyngula.org/index/weblog/comments/bicoid_evolution)