What is a genotype?

A genotype refers to the genetic makeup of an organism. It is encoded in the organism’s DNA and determines specific traits of the organism. 

DNA is organized into genes, and each gene can exist in different versions, called alleles. An organism’s genotype is determined by the combination of alleles it inherits from its parents. The genotype is responsible for influencing the phenotype, but external factors like environment and epigenetics also play a role. Not all organisms with the same genotype will look identical, nor do all individuals that appear similar necessarily share the same genotype. The presence of a dominant allele in the genotype ensures that the dominant trait will be expressed, regardless of the other allele.

Genotypes can be affected by mutations, but only heritable mutations (those passed down from parents) impact the genotype. Somatic mutations, which are acquired during an organism’s lifetime, do not bring about changes in the genotype. The genotype remains constant throughout an individual’s life unless altered by mutations, and phenotypic changes do not affect the genotype.

Determining an individual's genotype involves specialized processes such as DNA sequencing, polymerase chain reaction (PCR), and restriction fragment length polymorphism (RFLP).