Protein is made up of 20 different amino acids. Each amino acid consists of a central carbon. This central carbon is bonded to an amine group (NH2), a carboxyl group (COOH), a hydrogen atom and an R group.
Amino acids can be linked together when the amine group of one amino acid is bonded to the carboxyl group of a different amino acid. The COOH donates an OH group and the NH2 donates a H. The OH and H come together to form a water molecule, so this process is called dehydration synthesis - water is removed to form something new. The bond which holds the amino acids together is called a polypeptide.
I don't know what your choices are, but I would imagine that the answer is the process of crossing over. Next time please provide the choices that you're given :)
