Genotype and Phenotype: What are they? Differences, Relationship and Environmental Factors

We are all unique; genetically identical and even monozygotic twins always have some variation in how they look and act.

This uniqueness results from the interaction between our genetic makeup inherited from our parents and environmental influences from conception.

Understand the genotype and the phenotype

Wilhelm Johannsen was a scientist who worked in Denmark in the late nineteenth and early twentieth centuries.

During a series of experiments, he observed variations in genetically identical beans. He concluded that the interpretation must be due to environmental factors and coined the terms “genotype” and “phenotype” in 1911.



The genotype is the genetic makeup of an individual organism. Your genotype works as a set of instructions for the growth and development of your body.

The word “genotype” is generally used when discussing the genetics of a particular trait (such as the color of the eyes).


The phenotype is the observable physical or biochemical characteristic of an individual organism, determined by genetic composition as by environmental influences, such as height, weight, and skin color.



The term “genotype” is generally used to refer to specific alleles. Alleles are alternative forms of the same gene that occupy the exact location on a chromosome.

At any given locus, there are two alleles (1 on each chromosome of the pair): you get one allele from your mother and one from your father.

The two alleles could be the same, or they could be different. Different alleles of a gene generally serve the same function.

For example, they encode a protein that affects the color of the eyes but can produce different phenotypes (for example, blue or brown eyes) depending on the set of 2 alleles.

For example, the ability to test PTC (a bitter-tasting compound) is controlled by a single gene. This gene has at least seven alleles, but only 2 of these are commonly found.

A capitalized “T” represents the dominant allele that confers the ability to taste: “dominant” means that anyone with 1 or 2 copies of this allele will be able to taste PTC.

The unflavored allele is recessive and is represented by a minuscule ‘t’ – ‘recessive’ means that an individual will need two copies of the allele not to be a taster.

Each pair of alleles represents the genotype of a specific individual, and in this case, there are three possible genotypes: TT (taster), Tt (taster), and tt (non-taster).

The genotype is homozygous if the alleles are equal (TT or tt). If the alleles are different (Tt), the genotype is heterozygous.

It is rare for one gene to determine one characteristic, as in the case of the PTC test (a monogenic trait). Most features are complex and have genes that affect them at more than 1 (polygenic) locus.

How environmental factors affect the phenotype

Your genes carry instructions for the growth and development of your body. However, environmental factors influence its phenotype during embryonic development and throughout its life.

Environmental factors vary and include diet, weather, disease, and stress.

Genetics or environment

With the PTC tasting example, scientists estimate that the gene controls approximately 85% of the flavor capacity. The environmental factors that play a role include how dry your mouth is or how recently you have eaten.

The degree to which its genotype is determined by its genotype is known as “phenotypic plasticity.” If the environmental factors significantly influence the phenotypic plasticity is high.

If the genotype can be used to predict the phenotype reliably, phenotypic plasticity is low.

In general, the amount of influence that environmental factors have on their last phenotype is a much-debated scientific topic.

It is often referred to as the nature (genes) vs. nutrition (environment) debate. Scientists often study monozygotic (identical) twins to investigate the genotype/phenotype relationship.

In conclusion, its genotype or genetic composition plays a critical role in its development.

However, environmental factors influence our phenotypes throughout our lives, and it is this continuous interaction between genetics, and the environment makes us unique.