7 Differences Between Genotype and Phenotype - Summary and Examples

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The expression of life begins from the genes. It is these that determine the physical traits of a person, the behavior of each individual and their biochemistry. Some are the genotype and others, the phenotype. While they are closely related, they are not the same. In this Green Ecologist article we will explain the main differences between genotype and phenotype, as well as their definitions and practical examples so that you can understand their importance.

Definition of genotype and phenotype

As we have mentioned, both genotype and phenotype are related. But, even so, it is not the same concept. Next, we are going to explain in more detail what a genotype and a phenotype are.

Genotype

The genotype in biology is the hereditary content, that is, the genetic makeup of an organism. It can be represented in Mendelian factors, such as alleles, in genes, or in whatever representation is being used for genetic determinants. It can also refer to the set of characteristic genes of a species.

Phenotype

The phenotype in biology are the elements expressed by genes. The genotype contains genetic information that must be manifested in specific elements and, these elements, is what we know as the phenotype. That is, the genotype dictates phenotype. The word phenotype comes from the Greek phainein, which means to be visible. It is understood then that the phenotype is the visibility of the genes.

The elements to be expressed phenotypically can be physical features, as the concept was initially created by Mendel during his pea experiment, as it can also be a biochemist, developmental or even behavioral. We cannot say that the phenotype are visible characteristics, since genetic expression can occur at levels not visible for man, as is all the complex machinery that occurs at the cellular level.

Here are seven differences between phenotype and genotype.

The genotype comprises the genes and the phenotype the expression of the components

The genotype is stored as DNA, in sequences created by nucleic bases. These are reduced to four:

• Adenine
• Thymine
• Cytosine
• Guanine

The combination of these four bases, arranged in complementary pairs, creates genes. But the phenotype is expressed in a huge number of components. They can range from enzymes, hair color, reproductive behavior, size, life span, circadian cycle, among many others.

The genotype is unique, the phenotype can be the same

Same phenotypes may exist for different genotypes. The genotype includes the genetic information that an organism represents, both recessive and dominant genes:

• The recessive genes they require to be homozygous to be expressed.
• The dominant genes they can be heterozygous.

When they have a dominant heterozygous gene, they express the phenotype of the dominant gene and not that of the recessive one. You will find an example of this below. The phenotypes show only heterozygous genes dominant or recessive.

The genotype is transmitted, the phenotype is expressed

Organisms receive genetic information from their parents, with sequences of both parts selected by genetic recombination. On the other hand, the phenotype and its expression is the task of the daughter organism.

If you want to know more, we recommend that you take a look at this other article about genetic recombination: what it is and examples.

Genotype is not visible, phenotype is

The genotype contains the fundamental information packed in the form of DNA. This information must be expressed so that it can act within time and space. The phenotype is the expression of the genotype, which although it is not visible as such, taking into account what we raised as phenotypic characters previously, yes it is tangible and it is decoded.

The genotype cannot be modified by the environment, the phenotype can

Although the genotype has certain characteristics that are going to be expressed, for example in physical traits, complexion or skin color, the environment to which the phenotype can be modified, such as if an individual is sedentary, their physical structure will change.

It is important to mention that there are those who affirm that only the phenotype can be modified by the environment, but recently it has been discovered that the environment does have an effect on genes. This science is known as epigenetics and shows that both the habits we have, as well as the eating habits (the use of tobacco), among others, can turn genes on or off in organisms.

An example of this are alcoholics, who have a vitamin deficiency and, therefore, there are methylations in the DNA where it should not be, which activates genes of multiple diseases, including cancer.

Finally, it is worth recalling that the genotype is unchanged, there is only influence on how the genes that already exist in the genotype are expressed.

The phenotype depends on the genotype, but not vice versa

The phenotype is expressed by the genotype, there can be no characteristics that have not been previously determined by the genotype. The phenotype cannot dictate how the genes will act.

The phenotype always expresses something tangible and concrete, the genotype does not

The genotype may present instructions to express the specific genes, but there are also sequences that have regulatory instructions, that is, that turn genes on or off. The phenotype is expressed as tangible mode, but the genotype not only contains information for the traits, it is also regulatory.

Genotype and phenotype examples

Next, we are going to present two examples of genotype and phenotype that serve to see the differences that they entail.

Mendel's Pea Experiment

The most useful example to explain genotype and phenotype is Mendel's pea experiment, the initiator of studies of heredity. Mendel noted that peas had certain physical characteristics and that something must dictate that they were so. The phenotype of peas was the physical characteristic: smooth or rough. The smooth ones had R genotype, so if they were crossed pollen R with ovules R, they would give RR peas, that is to say smooth. The rough peas have genotype r. Now, if you take an egg with genotype R and smooth phenotype, and a pollen with genotype r and rough phenotype, it would have an Rr genotype.

The genotype written in capital letters always corresponds to the dominant gene and the recessive gene is written in lower case. The result of the progeny will be smooth phenotype, as this is the dominant gene.

Hair Color in Shorthorn Cattle Crossing

Another example of phenotype and genotype can be applied to hair color in the Shorthorn cattle cross. Bulls of genotype RR have red hair and cows of phenotype rr have white hair. When crossed, they will give progeny bulls, or cows, of the Rr genotype expressed as roan phenotype, that is, they have brown hair with evenly intertwined white hairs. When crossing back to this generation, the red phenotypes with RR genotype, roan phenotype with Rr genotype or white with rr genotype can be generated. This crossover helps to explain that of a same initial genotype there may be different phenotypes.

Not only can there be two alleles, but there can be multiple alleles for one gene. This is the case of human blood groups, in which there are phenotypes A with genotype AA or Aa, B with genotype A^BTO^B or A^Ba, phenotype AB with genotype AA^B, and phenotype O with genotype aa. The knowledge of the genotype helps to make them blood transfusions with the correct phenotypes otherwise, adverse incompatibility reactions could occur.

If you want to complete your knowledge on the subject, do not hesitate to visit this other article by Green Ecologist on cell biology: what it is and its importance.

If you want to read more articles similar to Difference between genotype and phenotype, we recommend that you enter our Biology category.

Bibliography

• Gómez-Pompa, A., Barrera, A., Gutiérrez-Vázquez, J., & Halffter, G. (1980). Biology: Unity, Diversity and Continuity of Living Things. Mexico City: National Council for the Teaching of Biology.
• Medawar, P., & Medawar, J. (1988). From Aristotle to Zoos: A Philosophical Dictionary of Biology. Federal District: Economic Culture Fund.