afit 370 million years ago, in the latter part of the Devonian Period, the ancestors of all land vertebrates emerged from the ocean and began to benefit from the untapped wealth found on the shore. This was a big step, literally and figuratively, and evolutionary biologists had long assumed that inducing the anatomical shift from the functional fin to the primitive tibia that enabled it to occur would require the coincidence of multiple genetic mutations. However, this may not be the case. A paper just posted in prison cellBy Brent Hawkins, Catherine Henck, and Matthew Harris of Harvard University, he suggests that the process was driven by a single genetic change of the smallest possible type.
The origin of tetrapods is best understood, since terrestrial vertebrates are known collectively to zoologists, the trio were looking at what happened to zebrafish (a common subject of experiments in developmental biology because they are small, transparent, and reproduce abundantly) modifying the genes of those fish. By looking at more than 10,000 mutant specimens, they observed that one group of mutants had an unusual pattern of bone in their pectoral fins. Instead of having four, they had six.
Interestingly, the additional pairs were some distance from the body, and the bones involved were parallel to each other in the way that the radius and ulna operate in the front of the quadrupedal (see figure). Furthermore, and most interestingly, the two new bones integrate precisely with the fin muscles and articulate well with the rest of the local skeleton. But what is more interesting is that this major anatomical transformation has resulted from the substitution of one type of protein molecule, called a link, of one of its essential amino acids.
The focal is an index protein. But it is not one, as much as the team can tell us by looking at the literature on embryogenesis, which has previously been linked by anyone to limb formation in vertebrates. However, the experiment they then conducted in mice, which involved eliminating the gene encoding the junction, led to related bone deformation in all four rodents’ limbs, not just the front ones. It is clear, then, that this protein actually plays a role in the formation of tetrapod limbs.
The most recent common ancestor of zebrafish and mice predates to the Devonian period. This gives a lot of time for the patterns of embryonic development to change in the lines leading to the two species – specifically, to change the way the fins of modern fish evolve. So the fact that the mutation that the team discovered at present only affects the pectoral fin does not exclude the possibility that it could also be stimulated, at that time, the pelvic fin of the fish ancestor of the mouse, reaching the bones now. Commonly known as the fibula and stalk. So it seems entirely possible that Dr. Hawkins, Hinky, and Harris found the source of the crucial change that enabled the rat ancestors – and humans too – to rush ashore and leave the sea behind.
This article appeared in the Science and Technology section of the print version titled “Get a Leg.”
Профессиональный решатель проблем. Тонко обаятельный любитель бекона. Геймер. Заядлый ботаник. Музыкальный новатор