Science creates chicken with a dinosaur paw

A dinosaur-like bone in your chicken leg: it can happen to you if scientists switch off a gene in that chicken.

Whoever has eaten a chicken leg knows that there is a long, thin bone in that chicken leg. This is the fibula (indicated in orange in the image below). It is one of the two long bones in the lower leg (and is located on the outside).

The different bones in the lower leg of a dinosaur, embryo of a chicken and a chicken. Click for an enlargement. Image: Universidad de Chile.

Dinosaur
Dinosaurs - according to many the ancestors of birds - also possess that bone, but it looks different (see the image above). Moreover, with dinosaurs this bone runs all the way down to the ankle. Somewhere in the evolution from dinosaur to bird this bone has lost its lower part and therefore the connection with the ankle and has become shorter than the other bone in the lower leg, the tibia.

Embryo
At least: you would think that if you were looking at an adult chicken for example. Things are different when you look at a chicken embryo. Already in the nineteenth century, researchers discovered that bird embryos first develop a dinosaur-like fibula that later becomes shorter than the tibia and grows into such a narrow bone that we know from chicken legs.

Gene
Scientists decided to find out how that transformation - from dinosaur bone to chicken bone - takes place in an embryo. They discovered it Indian Hedgehogplayed an important role in this. The researchers switched off this gene in chicken embryos and looked at what happened. The embryos were found to retain the dinosaur-like bone. They got a fibula that was just as long as the tibia and was attached to the ankle.

Shorter
What was also noticeable was that the other bone in the lower leg - the fibula - was shorter in the chickens whose gene was switched off. It indicates that a dinosaur-like fibula attached to the ankle inhibits the growth of the tibia and thus prevents tibia from becoming larger than the fibula. That is in line with fossil finds. The first life forms with a shorter fibula were birds at the beginning of the Cretaceous that lived side by side with the dinosaurs. These life forms had thin calf legs that were not attached to the ankle, but were almost as long as the tibia. The fibula first lost its end - which is attached to the ankle - and that made the evolution of tibia much longer than the fibula possible.

It is not the first time that researchers treat a chicken to a dinosaur-like trait. Previously researchers already provided a chicken with a dinosaur-like toe and snout. With the Jurassic Park-like activities, the researchers do not pursue commercial, but purely scientific goals, emphasizes researcher Alexander Vargas. “The experiments focus on one characteristic to test specific hypotheses. We do not only know a lot about the development of birds, but also about the transition from dinosaur to bird that we see in the fossil finds. That leads to hypotheses about their evolution and that can be explored in the lab. "

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