Although genes play an important role in human behavior, they exist within the context of a complex environment that is necessary for an organism to even exist. Environment includes all of the surrounding physical and social conditions and influences that affect the development of living things. Genetic material may be expressed differently depending on the environment. In other words, people's observable and measurable characteristics might not reflect their genetic heritage very precisely because of the experiences they have had.

To account for this gap between genes and behavior, scientists make a distinction between genotype and phenotype. Genotype is the individual's genetic heritage, the actual genetic material. Phenotype is the way an individual's genotype is expressed in observable, measurable characteristics. Phenotypes include physical characteristics (such as height, weight, and eye color) and psychological characteristics (such as intelligence and personality).

For each genotype, a range of phenotypes can be expressed. An individual can inherit the genetic potential to grow very large, but good nutrition will also be important to achieving that potential.

Or suppose that we could identify all of the genes that contribute to making a person introverted (shy) or extraverted (outgoing). Would measured introversion or extraversion be predictable from knowledge of specific genes? The answer is no, because introversion and extraversion are characteristics that are influenced not only by heredity but also by experience. For example, parents might guide a shy child to become more social.

1		A college student who has just described her friend as tall, blond, intelligent, and sociable has described her friend's _______________.
			A)	dominant traits
			B)	recessive traits
			C)	genotype
			D)	phenotype
2		A genetic counselor who has told a man that he is a carrier of an inherited disease has described an aspect of the man's
			A)	genotype
			B)	phenotype
			C)	karyotype
			D)	blood type
3		The expression of an individual's genotype in observable, measurable characteristics is the individual's .