(Please correct me if I'm wrong on any count here).
As I understand it, development requires the action of numerous genes and proteins. My textbook has described it as being almost reminiscent of a cascading sequence. It is comprised of:
- Maternal effect genes/Egg-polarity genes - These are cytoplasmic determinants from the mother.
- Gap genes
- Pair-rule genes
- Segment-polarity genes
- Homeotic genes (these determine what structures are placed where on the body axis).
- Other embryonic genes
The issue is my text only described 1 and 5 in any depth - items 2-4 are merely named. I don't know what 6 is, though I imagine these genes actually code for proteins that build the structures (e.g. eyes in Drosophila). The same is true for 2-4, which I believe are segmentation genes, in that they are responsible for directing segment formation.
Could someone please clarify what these actually are, and why they're given such (seemingly) unusual names?