Genotype and Phenotype 128 KEY TERMS AND IDEAS:

1. The genotype and phenotype of an organism can be affected by a variety of environmental factors.

(a) Define the term mutagen. Give an example of a mutagen, its origin, and its effect:

(b) Explain how the environment can affect an organism's phenotype without affecting the genotype. Use two examples to help you illustrate your explanation (use extra paper if you need to).

(c) Discuss the effect of point mutations on genes. Use a human example to explain the genotype and phenotype changes that can occur as a result of a base substitution (use extra paper if you need to).

(a) Explain what is meant by a metabolic pathway:

(b) Explain how phenylketonuria occurs and why people with the disorder must make modifications to their diet: