The correct answer to this question is A, Keratin. It is apart of the family of proteins. Not only does it make up the turtle's beak, but it also keratin can also be found in hair, claws, and hooves. It protects epithelial cells from stress and damage.
There are several types of keratins. a-keratins are found in vertebrates. In mammals, they form hair, horns, claws, and nails. b-keratins are found on reptiles and birds. This keratin is found on shells, feathers, and claws. In humans, the genome has 54 functional keratin genes encoded. They are located in two clusters of the chromosomes.
