Final answer:
New proteins can either increase or decrease the fitness of children depending on whether the mutations that produce them are beneficial or deleterious. Neutral mutations have no effect on fitness.
Step-by-step explanation:
New proteins can affect the fitness of children in different ways. Beneficial mutations that result in the production of new proteins can increase fitness, as they may enhance an organism's ability to survive and reproduce. On the other hand, deleterious mutations that lead to the production of faulty proteins can decrease fitness, as they may impair important cellular functions. Neutral mutations, which do not affect protein function, have no effect on fitness.