The expansion of the Hox gene groups and the
evolution of new functions for the genes enabled
animals to become more complex, and allowed
different segments of animals to diversify and
evolve special functions.
The way in which these genes are controlled can
also explain the diversity of animal forms within
closely related groups.
All vertebrates have a similar toolkit of Hox genes
but for example: clearly the body plan of a bird differs
from that of a monkey.
HOX GENE EXPRESSION
The specific regional functions of individual Hox genes largely reflect their
restricted expression patterns, the disruption of which can lead to
developmental defects and disease. Here, we examine the spectrum of
molecular mechanisms controlling Hox gene expression in model
vertebrates and invertebrates and find that a diverse range of
mechanisms, including nuclear dynamics, RNA processing, microRNA and
translational regulation, all concur to control Hox gene outputs. We
propose that this complex multi-tiered regulation might contribute to the
robustness of Hox expression during development.
So basically, Hox genes are like light engineers using different
combinations and intensities of a few primary colours to create a whole
range of different effects.