Genotype and phenotype

• All the genes present in an individual organism interact with the environment in which the organism grows and develops its observable appearance and character. These characteristics are its phenotype.
• The variation in the characteristics of individuals of the same kind may be due to differences in: • the genes they have inherited (genetic causes) • the conditions in which they have developed (environmental causes) • a combination of genes and the environment.
• Human height is an example of a characteristic determined by many genes, each with different alleles.
• The set of alleles that determine the height of a person is the genotype for that characteristic.
• Height is also affected by diet and exercise which are part of the environment in which an individual grows up.