What is genotype as defined in biology?

• A. The genetic makeup of an organism; the alleles it carries.
• B. The observable traits of an organism.
• C. The environment that interacts with genes.
• D. The complete set of genes in an organism's genome.

Answer: (A)

Genotype is the genetic makeup—the specific alleles an organism carries at its gene locations. It represents the inherited information in the DNA that helps determine potential traits, even if those traits aren’t always visible. The phenotype is the observable trait, which results from genotype interacting with development and the environment. The complete set of genes in a genome describes what could exist, but genotype refers to the actual allelic versions present in an individual rather than just the list of genes. For example, at a coat color gene, having two brown alleles versus one brown and one white allele shows different genotypes that can influence the phenotype.