Genotype vs Phenotype

Team Biology at
Created by: Team Biology at, Last Updated: April 25, 2024

Genotype vs Phenotype

Genotype refers to an individual’s unique DNA sequence, specifically the variants inherited from each parent for a particular gene. In contrast, phenotype is the observable expression of the genotype, shaped by the interaction between genetic makeup and environmental factors. The relationship between genotype and phenotype is complex and not always predictable, often leading to variations in the manifestation of genetic conditions.

Factors such as reduced penetrance and variable expressivity contribute to these discrepancies. Reduced penetrance means that not all individuals with a genetic variant will exhibit the associated condition, influenced by a mix of genetic, environmental, and lifestyle factors. For instance, familial cancer syndromes often show reduced penetrance, complicating risk predictions for relatives.

Differences Between Genotype and Phenotype


A genotype is the specific combination of alleles an individual inherits for a particular gene, located at a fixed position on a chromosome known as a locus. Genes, sections of DNA, encode traits through the arrangement of nucleotides—each consisting of a phosphate group, a sugar, and a base. These genes can exist in various forms, or alleles, which differ between organisms. In diploid organisms, the genotype can be homozygous, inheriting two identical alleles, or heterozygous, inheriting two different alleles at the locus. The expression of these alleles, whether dominant or recessive, ultimately determines the traits manifested by the individual.


A phenotype encompasses all the observable characteristics of an organism, influenced by both its genetic makeup (genotype) and various external factors. Unlike the genotype, which parents directly inherit, the phenotype does not solely derive from parental genes. It results from the interplay between the genotype and additional elements such as epigenetic modifications, environmental conditions, and lifestyle choices. This complex interaction ensures that even organisms with similar genotypes can display significantly different phenotypes.

Differences Between Genotype and Phenotype
DefinitionGenotype refers to the genetic makeup of an organism; the specific alleles present at a given locus.Phenotype describes the observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
DeterminationDetermined by the genes inherited from the parents.Determined by the genotype and environmental factors, including diet, lifestyle, and climate.
VisibilityNot directly observable; can only be assessed through genetic tests.Directly observable traits such as height, skin color, and eye color, or measurable characteristics like blood type and enzyme activity.
VariabilityRemains constant throughout life. Genes received at conception are unchanged.Can change over time. For instance, weight and skin tanning can vary significantly due to environmental factors.
ExamplesA person carrying a recessive allele for cystic fibrosis, which might not be expressed.A person actually exhibiting symptoms of cystic fibrosis due to the presence of two recessive alleles.
InheritancePassed down from parents to offspring through genes. Each parent contributes half of the offspring’s genotype.Not inherited directly. While genetic potential is inherited, the phenotype is the expression of that potential under particular environmental conditions.
Change due to MutationCan change if a mutation occurs in the DNA sequence. Such changes can be inherited.Can be affected by mutations in the genotype, but also by new environmental conditions; not all changes in phenotype are inheritable.
StudyStudied in genetics through breeding experiments, DNA sequencing, and molecular biology techniques.Studied through observations of physical traits, physiological responses, and behaviors in various environmental contexts.
PredictionGenotype can be used to predict possible phenotypes but does not guarantee specific outcomes due to environmental influences.Phenotype can give clues about genotype but cannot reveal exact genetic composition without genetic testing.

Key Similarities Between Genotype and Phenotype

  • Basis in Genetics: Both genotype and phenotype are fundamental concepts in genetics. The genotype acts as the genetic blueprint contributing to the phenotype, the physical expression.
  • Role in Heredity: Both play crucial roles in the study of heredity and evolution, helping to understand how parents pass traits to offspring.
  • Influence on Traits: Each influences the traits of an organism. While an organism carries its genotype as a set of genes, the phenotype represents the expression of these genes, evident in the organism’s physical appearance and behavior.
  • Subject to Study: Researchers study both genotype and phenotype in genetics and biology to understand how organisms inherit traits, how these traits manifest, and how variations occur.

Key Differences Between Genotype and Phenotype

  • Definition and Observation:
    • Genotype: An organism’s genetic makeup, a set of genes in the DNA, is not directly observable and requires genetic testing for determination.
    • Phenotype: An organism displays observable traits or characteristics such as morphology, development, biochemical or physiological properties, and behavior.
  • Influence of Environment:
    • Genotype: The environment does not influence the genotype. The genetic makeup remains unchanged under external conditions.
    • Phenotype: Both genetic factors and environmental conditions significantly influence the phenotype. Environmental factors can modify how genes express.
  • Variability:
    • Genotype: The genotype stays constant throughout an organism’s life. Only mutations can change it.
    • Phenotype: The phenotype can change throughout an organism’s life in response to environmental conditions. For instance, sun exposure can alter skin color, and exercise can modify body composition.
  • Transmission:
    • Genotype: Parents directly pass the genotype to their offspring, with each parent contributing half of the genetic makeup.
    • Phenotype: The phenotype is not directly inheritable.
    • While inheritance determines the potential for certain phenotypes, the actual phenotype results from the interaction between genotype and environment.
  • Predictive Power:
    • Genotype: It can predict potential phenotypes but cannot guarantee them due to environmental influences.
    • Phenotype: It provides clues about an individual’s genotype but cannot pinpoint the exact genetic makeup without genetic testing.


What is the Difference Between Genotype and Phenotype?

Genotype refers to an organism’s genetic makeup, while phenotype is the observable expression of those genes.

What is Phenotype Example and Genotype?

Phenotype example: blue eye color. Genotype example: BB or Bb genes for eye color.

What are 5 Examples of Genotypes?

  1. AA (homozygous dominant)
  2. Aa (heterozygous)
  3. aa (homozygous recessive)
  4. BB (homozygous dominant)
  5. Bb (heterozygous)

Is AA a Genotype or Phenotype?

AA is a genotype, representing a specific set of alleles in an organism’s DNA.

What are the 3 Genotypes?

The three genotypes are homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa). Each represents different genetic combinations from parental alleles.

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