Hox genes allow animals to have complex body plans with specialized segments through their controlled expression patterns. A diverse range of regulatory mechanisms, including nuclear dynamics, RNA processing, microRNAs, and translational control, work together to ensure robust Hox gene expression during development. Disruptions to this complex multi-tiered regulation of Hox genes can lead to developmental defects.

1. 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.
Hox genes

2. 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 genes

3. 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.
Hox genes

4. Last words
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.
Hox genes