Genetic Control of Development

As transcription factors, the homeotic gene products must bind to DNA. Sequence analysis of both gene and protein has revealed that all share a 180-nucleotide DNA stretch, termed the homeobox, the sequence of which has remained almost unchanged over many millions of years of evolution. It codes for a 60-amino acid long DNA binding region, called the homeodomain. The homeodomain sequence of antennapedia and the mouse homeotic gene Hox B-7 differ by only two amino acids, despite having diverged several hundred million years ago.