What are Genotypes? – Definition & Examples

The concept of dominance was one of Gregor Mendel’s most significant contributions to heredity research. Because a heterozygote offspring can have the same phenotype as the parent homozygote, Mendel came to the conclusion that some hereditary qualities dominated over others. The relationship between genotype and phenotype, on the other hand, is rarely as straightforward as Mendel’s dominant and recessive patterns. Biologists began to find a range of associations between alleles that code for the same feature as the study of inheritance went beyond the seven qualities Mendel initially investigated and covered animals other than pea plants. These allelic interactions were not primarily recessive or dominant, and they contributed significantly to our understanding of how genotype influences the phenotype.

Genotype Definition

An organism’s genotype is the chemical makeup of its DNA, which gives rise to its phenotype, or visible characteristics. A genotype is made up of all the nucleic acids that code for a specific trait in a DNA molecule. The phenotype, or outward appearance, is the outcome of protein interactions generated by DNA. Modern DNA analysis tools have made determining which DNA segments are responsible for specific traits much easier.

Different alleles, or forms, exist in a genotype. Mutations in the DNA produce distinct alleles, which might result in positive or harmful modifications. In bacteria, DNA is arranged in a ring, and each genotype has only one allele. When an allele mutates in a favorable way, the organism reproduces more and the genotype of the population increases. In sexually reproducing organisms, each organism has two alleles, which can interact with one other and other genes in complex ways. In these alleles, mutations can occur, new combinations can emerge during meiosis, and a limitless amount of variation can be formed. The great variety of life on Earth is due to these genotype combinations.

How do Genotypes Come About?

Chromosomes, the closely packed DNA structures in the cell nucleus, contain genes. Chromosomes come in pairs in sexually reproducing organisms, one from the mother and one from the father. Each person, for example, will have two ‘Chromosome 1s’ and two ‘Chromosome 2s.’

Because they carry the same genes, chromosomes in a pair (excluding sex chromosomes) are called homologous chromosomes. For example, both chromosome 8s have the gene that affects whether a hairline becomes a widow’s peak, among other things.’

Each gene always has two copies, one from each parent. A gene, on the other hand, can have several alleles. Alleles are different variants of the same gene. Genotypes are formed by the combination of alleles inherited from both parents.

Genotype and Alleles

Alleles can interact in a variety of ways to alter distinct parts of a living entity. In cats, for example, the length of their fur is determined by a gene that comes in two forms: short and long. Cats with two short alleles have short fur. It has long fur if it has two long alleles. It has short hair if it has one of each. The short allele is considered to be dominant over the recessive long allele in this scenario.

When just one allele is required to see a trait in a diploid organism, the trait is dominant. Geneticists use a capital letter to designate dominant alleles and a lowercase letter to denote recessive alleles. In the case of cat fur length, “L” stands for “short hair allele” while “l” stands for “long hair allele.”

There is no such thing as a dominant or recessive allele. Two alleles may be codominant—that is, they combine to form a trait—in some cases, such as blood type. If someone possesses both an A and a B allele, they have the AB blood type. Sometimes alleles are only partially dominant. Snapdragons, for example, have a pink blossom due to a red gene and a white allele.

Heterozygous and homozygous genotypes are two types of genotypes. One copy of one allele and one copy of the other allele are seen in heterozygous genotypes. Two copies of the same allele are found in homozygous genotypes. Cat coat length is determined by the heterozygous genotype Ll, with one allele (L) coding for a short coat and one allele (l) coding for a long coat. For cat coat length, there are two homozygous genotypes: LL (homozygous dominant) and ll (homozygous dominant) (homozygous recessive).

The genotype ratio is the probability of offspring possessing a specific genotype. A graphic known as a Punnett square can be used to calculate this probability. This is essentially a grid with the genotype of one parent as a column and the genotype of the other parent as a row.

There are two rows and two columns, one for each allele, if the diagram depicts one gene with two alleles. The allelic combinations in the rows and columns show the offspring’s likely genotypes.

Related Biology Terms you Need to Know


The ability to disguise the consequences of a recessive allele is known as dominance.


An allele that has phenotypic consequences only when another recessive allele is present.


A genotype with two types of alleles is known as heterozygous.


A genotype with only one allele type.

What are the different types of genotypes?

Homozygous recessive (pp), homozygous dominant (PP), and heterozygous genotypes are the three types of genotypes (Pp). The phenotypes of homozygous dominant and heterozygous genotypes are identical.

How are alleles different from genotypes?

Alleles are gene variants, whereas genotypes are the sets of genes responsible for specific phenotypes. Both, however, dictate biological features, albeit the copies may not be identical.

How are genotype and phenotype related?

Although genotype and phenotype are two distinct entities, they are closely related. The physical qualities that are noticed in an organism as a result of the expression of an individual’s genes are referred to as phenotypes. An individual’s phenotype is determined by their genetics.

Are genotypes heterozygous?

Homozygous and heterozygous genotypes exist. Dominant features are expressed by heterozygous genotypes. When a genotype has two recessive alleles, a recessive characteristic is expressed.

What factors determine the genotype of an individual?

The environment in which an organism lives, as well as the interior body environment of an organism, such as hormones and metabolism, determine an individual’s genotype.

How do you identify a genotype?

A Punnet square can be used to identify a genotype. It aids in calculating the likelihood of an offspring’s genotype depending on the genotype of the parents.

Examples of Genotype

Eye Color 

Scientists often represent genotypes with single letters, or two letters in the case of sexually reproducing animals that receive one allele from each parent, despite the fact that a genotype consists of multiple nucleic acids. The feature of eye color, for example, could be represented by the letter “E.” Capital letters will be used to denote the dominant trait’s variants or alleles. As a result, “E” will stand for brown eyes. Recessive traits are denoted by lowercase letters. We can designate the allele for blue eyes “e” because it is recessive to the allele for brown eyes.

Example of Genotype

Brown eyes are shared by a pair of parents. Brown eyes only reveal a person’s phenotype, not their genotype. 

The parents could be “Ee,” “EE,” or a combination of the two. Even if the father has a recessive “e” allele, a single “E” allele in the genotype will result in the brown-eyed phenotype. 

A child is conceived by the parents. The child’s eyes are blue. Because only two recessive alleles can create blue eyes, this indicates that the child is homozygous recessive, or “ee.” This reveals a lot about the parents as well. With two “e” alleles, the baby received one from each parent. 

As a result, although possessing the brown eyed phenotype, each parent has one “e” allele to pass on. This indicates that both parents are heterozygous for the “Ee” genotype. 

If either parent is homozygous dominant, “EE,” the kid will get at least one dominant “E” gene, giving it brown eyes.

Curly hair

The genotype for curly hair would be HH or Hh if we take the genotype for hair type as H for dominant trait and h for a recessive trait.

The protein that promotes curly hair is coded for by this genotype.

If the genotype is HH, the person will have curly hair; however, if the genotype is heterozygous, the hair will be wavy, which is a cross between curly and straight hair.

Because straight hair is a recessive trait, the genotype would have to be hh for the hair to be straight.

Individuals with the heterozygous condition have the curly hair trait in complete dominance.

Cystic Fibrosis

Cystic Fibrosis is a disease that affects the lungs. For a long time, no one knew why some children’s airways became clogged with thick mucus, making them short of breath and wheezy. Other symptoms included an inability to metabolize meals efficiently, flatulence, and weight loss in the children. Many children perished at a young age before recent discoveries in medical and genetic sciences. Cystic fibrosis was discovered to be caused by a mutation in a gene that creates salt channels across cell membranes after years of research. These salt channels, also known as ion channels, are responsible for maintaining pH levels in cells, removing waste, and removing nutrients from the intestines.

Cystic fibrosis patients have a homozygous recessive genotype. In other words, they have two copies of the gene that produces certain ion channels with the non-functioning allele. While having a heterozygous genotype, some persons, known as “carriers,” can have a functioning, normal phenotype. This means that a non-functioning allele can be passed down to a child by a carrier. Unwittingly, two carriers can pass on the non-functioning gene, resulting in a non-functioning homozygous recessive genotype for the offspring. If one or both carrier parents pass on their favorable allele, the child will be free of cystic fibrosis symptoms. The child will be a carrier if they acquire one functional and one non-functional allele. If a child receives two functioning alleles, they will not be carriers.

However, offspring of parents who are both carriers will have a genotypic ratio of 1 normal: 2 carriers: 1 cystic fibrosis genotype. A Punnett square can be used to count this genotypic ratio. Separate the heterozygous parents’ specific alleles by placing them on the sides of the square (Aa and Aa below). Then simply fill in the boxes with the two alleles that each possible child would receive. The genotypic ratio is 1AA:2Aa:1aa, which can be rapidly determined by counting. The phenotypic ratio in this situation would be 3 normal: 1 cystic fibrosis.

Other examples of genotype include:

  • Hair color
  • Height
  • Shoe size

Phenotype Definition

  • In genetics, phenotype refers to all observable features in organisms that are the outcome of the genotype’s interaction with the environment.
  • The word phenotype comes from the Greek word pheno, which means “to observe.” Phenotypes are used to describe the observable properties of organisms, such as their height and color.
  • An organism’s phenotype includes its morphology, physical shape and structure, development and behavior, biological and physiological qualities, and even the organism’s products.
  • As a result, phenotypes are utilized to discern discrepancies in DNA sequences between people who have different heights.
  • An organism’s phenotype is determined by two components: the genome’s expression, or genotype, and its interaction with environmental stimuli.
  • An organism’s phenotypic can be influenced by one or both of these variables.
  • Environmental, physiological, and anatomical changes connected with age create phenotyp variation even within an individual.
  • Natural selection is based on phenotype variation, in which the environment favors the survival of more fit individuals over the others.
  • Individuals with identical genes may display different phenotypes if they are exposed to diverse environments, as seen in twins.
  • As a result, evolution via natural selection would be impossible without phenotypic variety.
  • The concept of phenotyp variation may have an effect on an individual’s genetic makeup. Silent mutations, which do not modify amino acid sequences but change the frequency of guanine-cytosine base pairs, are one example of this.
  • This modification changes the genome’s G-C composition, which increases thermal stability and allows the organism to survive in high-temperature conditions.
  • The blood group, eye color, and hair texture, as well as hereditary illnesses in people, pod size and color of leaves, beak birds, and other phenotypes, are all examples of phenotypes.

Phenotype examples

Melanin production

  • Melanin production in humans is regulated by certain genes; consequently, changes in melanin production are attributable to differences in organism genotype.
  • Although various genes regulate the distribution of melanin throughout the body, only one gene influences its production.
  • As a result, individuals with a certain genotype may have no melanin production at all, resulting in albinism.
  • As a result, albino persons usually have skin that is white or pink in color.
  • Albinism is a trait caused by a specific genotype, and because albinism has a vast gene pool, examples of albinism can be found in a variety of populations.
  • Albinism is thought to be common in some species.

Mendels’ Peas

  • As part of his research, Mendel looked at a variety of phenotypes in peas. Those phenotypes provided the foundation for almost all of his discoveries.
  • Green and yellow-colored peas were researched when it came to pea hue. He discovered that crossing yellow and green peas resulted in peas that were half yellow and half green, with considerable variance in certain generations.
  • He calculated the ratios of different phenotypes in different generations based on this.
  • A specific gene codes for pea coloring, which results in a yellow tint. The pea’s hue changed to green when this gene was missing.
  • As a result, the dominant allele is yellow, whereas the recessive allele is green.

Genotype vs. Phenotype

The term “genotype” refers to a person’s entire set of genes. All of the observable features for which the genes code are referred to as phenotypes. To put it another way, the genotype refers to genetic information, whereas the phenotype relates to observable qualities such as traits.

Eye color and hair color are examples of phenotypes in humans. Coat length is an example of a phenotypic in cats. The genotype that corresponds to the phenotype of short coat length is either LL or Ll, whereas the genotype that corresponds to the phenotypic of long coat length is ll.

Phenotypes are influenced by genotypes, but these two factors are not always fully connected. Environmental factors influence phenotype and a single phenotype may be the product of multiple genotypes. Short cat hair, for example, can be caused by one of two genotypes: LL or Ll.

Key Differences (Phenotype vs Genotype)

Basis for ComparisonPhenotypeGenotype
DefinitionA phenotype is any trait that can be observed in a living organism as a result of the genotype’s interaction with its environment, as defined by genetics.Genotype is a genetic term used to describe an individual’s genetic composition, which includes heritable genes.
ObservablePhenotypes are characteristics that can be observed on an organism’s body.Genotypes are hidden within an individual’s chromosomes and hence cannot be seen.
InheritedPhenotypes are not passed down across the generations.During sexual reproduction, an individual’s genotype is passed down to their children in part as one of two alleles.
Consists ofPhysical shape and structure, development and behavior, biological and physiological features, and even the organism’s products are all examples of phenotypes.A genotype is a collection of an organism’s inherited features that may or may not be manifested in subsequent generations.
Affected byA phenotype is influenced by genetics and environmental factors.The genotype is influenced by the individual’s genetic makeup, which is influenced via sexual reproduction. Heritable mutations may also impact the organism’s genotype.
RelationA genotype that produces the same phenotype may or may not produce the same phenotype.Unless there are heritable mutations, the same genotype always results in the same phenotype.
Determined byThe phenotype of an organism can be determined easily by observation.Genotypes can be determined in a variety of scientific methods including PCR and RFLP.
Environmental factorsEnvironmental factors influence phenotypes.Environmental factors do not affect genotypes.
ChangesAn individual’s phenotype may change throughout his or her lifetime, such as the color of his or her hair.All genotypes remain constant throughout the lifespan of an individual.
ExamplesA variety of phenotypes can be seen in various organisms such as blood type, eye color, and texture of hair, as well as genetic diseases in humans, pod size and color of leaves, or beak shape of birds.Some of the genotypes that can be seen in different animals include homozygous alleles such as TT for height, heterozygous alleles such as Tt for height, and homozygous alleles such as BB for eye color.

Confusion of Concepts

It’s easy to get confused with the notions. Consider the concept of phenotypic plasticity, which is a so-called rapid response adaptive mechanism that allows an organism to change in response to external stimuli, resulting in multiple phenotypes. Although the genome is not involved in this method, changes in gene expression are a part of it. Given that certain definitions of phenotypic plasticity pertain to a genotype’s environmental sensitivity, it might be difficult to define language precisely.

Environmental sensitivity does not imply that the genome responds directly to the environment, which is why the term genotype is used here. Phenotypic plasticity, on the other hand, refers to phenotypic changes that occur without a permanent genetic change in the individual. It is the resulting component of the GxE (genotype by environment) interaction and is defined as the range of phenotypes that an organism can express as a function of its environment.


In the preceding content, we looked at two perplexing terms: phenotypes and genotypes, and how they differ from one another. We also looked at their relationship and interdependence.

Leave a Comment