Genotype and phenotype

The genotype is the genetic code of the cells of an organism, which determines the characteristics of an individual. The phenotype is the trait that we can observe, either as a physical characteristic or as a behavior.

The phenotype depends on the genotype, and can additionally be influenced by environmental and nutritional factors.

GenotypePhenotype
DefinitionGenetic composition of an individual determined by DNA sequence.Detectable manifestation of genotype. Observable traits, such as hair color, bone size.
EtymologyFrom the Greek genos = birth and ty pos = mark: birthmarks.From the Greek phainein = show and typos = mark: the marks that are shown.
Depends onThe hereditary information that was given to an individual by his parents.Genotype

Environment

The nutrition

InheritanceHereditarily transmitted from parents to their offspring.Heredity plays a part.
ContainsAll hereditary information of an individual.Observable features.
MeasurementBiological tests and genetic sequencing.Through the senses, such as vision or touch.
ExamplesSequence of recessive and dominant genes for blood groups.Blood groups A, B, AB and O that are expressed in human red blood cells.

Definition of genotype and phenotype

The genotype is made up of the genetic makeup of a cell. The genotype of an individual includes all the genes that may or may not be expressed, that is, that produce a certain protein.

Most genes have at least two alternative forms, called alleles . When the alleles are the same, the individual is homozygous; when the alleles are different, the individual is heterozygous.

For example, in pea plants, the gene for flower color has two alleles: the white allele and the purple allele. If the pea plant has two purple alleles, it is homozygous; if the plant has a purple and a white allele, the plant is heterozygous.

The phenotype refers to a trait that can be observed as physical or behavioral characteristics. In the case of pea plants, the phenotype of a plant with two purple alleles will be purple flowers, the phenotype of a plant with two white alleles will be white flowers. In the case of plants with a purple allele and a white allele, the phenotype will be purple flowers, because the purple allele is dominant.

You may be interested in seeing Gene and allele .

Identification of genotype and phenotype

The genotype can be identified through various chemical tests that mainly consist of determining the genetic makeup of the individual. These tests include DNA analysis tests, paternity tests, and polymerase chain reaction (PCR), among others.

The phenotype can be identified by observing the characteristics of the individual. Sometimes these features cannot be seen with the naked eye. For example, to determine the blood group phenotype of human red blood cells, a laboratory test is required.

Relationship between genotype and phenotype

The genotype of an individual comprises his entire genetic makeup. This includes dominant or recessive genes, regulatory sequences and what is known as junk DNA, which is DNA that is not yet known what it is for.

The phenotype is the result of the genes that can be expressed and of the external factors that affect their expression: environmental, nutritional and chemical factors.

If we make the analogy of genotype and phenotype with a book, the genotype is the whole book: the leaves and what is written on them. The phenotype, on the other hand, is what we read in the book.

You may be interested in knowing about genes and chromosomes .

Genetic heritage

In sexually reproducing organisms, sex cells or gametes have half the genetic makeup of the species. By combining a female gamete with a male one, they complete the individual’s genetic makeup. So, the genotype of this individual is the result of the combination of the genotypes of its procreators.

Although the phenotype is determined by the genotype, and this by heredity, there are other factors that affect phenotypic manifestations. For example, if a baby does not receive adequate nutrition during his first stage of life, he may not reach the height that was determined in his genes.

We also have the case of identical twins that have the same genotype, but can present different phenotypes.

An individual’s phenotype can change during his lifetime, depending on which genes are expressed and how external conditions affect them. For example, a young child with green eyes may turn blue eyes after a while.

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