What is the difference between a genotype and a phenotype?

• A. Genotype is physical trait; phenotype is genetic makeup
• B. Genotype is genetic makeup; phenotype is observable trait
• C. Genotype is environment; phenotype is diet
• D. Genotype is chromosome count; phenotype is eye color

Answer: (B)

The main idea is that genotype refers to the genetic makeup—the specific genes and alleles an organism carries—while phenotype is the observable trait—the characteristic you can see or measure. The genotype gives the potential for certain traits, and the phenotype is how those genes are actually expressed in the organism. For example, a plant might have genes for tall growth, but if it doesn’t get enough nutrients, its height (the phenotype) may end up being shorter. The environment can influence how a genotype is expressed, but the genetic makeup itself is the genotype, while the visible traits are the phenotype. Other descriptions that swap these terms or treat the environment as the genotype aren’t correct.