The Hox genes, all of them:
What do humans have in common with worms, flies and rodents? If you said, "not much," you're right. But not as "right" as you might think. During the early 1980s, scientists discovered that most of the genes in fruit flies that control the identity of different body parts -- a head, wing, or other structure -- are remarkably identical. The genes contain short sequences of deoxyribonucleic acid (DNA), which is found in every living cell and forms the "blueprint" for all organisms. Surprisingly, researchers discovered that the DNA sequence they had found in flies, called the homeobox, was common to genes that direct development of body structure in virtually all animals, including worms, flies, birds, mice and humans. "Homeo" is derived from the Greek word for similar; "box" refers to the clearly defined sequence, as though in a box.
Since the homeobox sequence stayed very similar during millions of years of evolution in many species, scientists suspected it must be important to life. They soon learned that the part of the protein it encodes can bind to DNA in a way that turns other genes on and off.
Even more surprising, scientists found that many genes containing the homeobox sequence, called hox genes, are lined up in clusters along chromosomes -- large strands of genetic material -- in an order that parallels the body part they control. On a fly chromosome, hox genes closest to one end control formation of the head, while the next ones in line control the upper body. At the other end of the cluster are genes controlling abdomen formation. When all these genes work correctly, the proteins they produce act together to ensure that each organism's body parts are made in correct locations. Hox genes also control development of parts of the central nervous system, including different regions of the brain.
Researchers concluded that hox genes are "master regulators" for the organization of the body. When the function of one of these genes is changed due to a genetic mutation or other factor, the wrong body part will develop in a given place. A fly, for example might grow a leg in the middle of its head.
A brief note, all the genes which evolutionists call 'pathways' are from multi-cellular creatures which arose during the Cabmrian explosion. The Hox genes are obviously a necessary requirement for multi-cellular organisms, that such a universal set of genes could have arisen in such a short time to become the basis of just about all multi-cellular animals, and that they could serve as building blocks for future species functions, shows pretty well that they could not have arisen either at random or due to 'selection' but could only have arisen by design.
It looks like the trend may be that many of the regulator genes appear from the earliest, e.g. like pre-programmed adaptation ability.
Are the Hox genes conserved across phyla like the eyeness gene, i.e. between human and mouse, 100% identical and between human and drosophilia, 94%? This is evidently the astonishing observation; IOW, it puts more emphasis on pre-programmed adaptation capability and less on random mutation branching away from the common ancestor(s).