What is phenotype?

• A. Genetic makeup
• B. Observable trait
• C. Chromosome number
• D. Allele frequency

Answer: (B)

Phenotype is the observable characteristics of an organism—the traits you can see or measure, such as eye colour, height, or blood type. It reflects the physical expression of the genotype and can be influenced by the environment, so the same genetic makeup can sometimes lead to different appearances under different conditions. The genetic makeup describes the set of alleles an individual carries (their genotype), which is not itself the visible trait. Chromosome number is about the count of chromosomes in cells, a cytogenetic feature rather than a trait. Allele frequency refers to how common a particular gene variant is in a population, not an individual's appearance. So phenotype is the observable trait resulting from how genes are expressed in a given environment.