Allele, Allelomorph

Allele (Allele), Allelomorph (Allelomorph) - one of two or more alternative forms of a gene, only one of which can be present on a chromosome. Two alleles of one single gene occupy identical positions on homologous chromosomes. If two alleles are the same, then the individual is homozygous for that gene; if different, then heterozygous. See also Dominant, Recessive. - Allelic.

Alleles and allelomorphs: key concepts of genetics

Alleles and allelomorphs are important concepts in genetics that describe one of two or more alternative forms of a gene. Only one of these forms can be present on each chromosome, and they have different phenotypic manifestations.

What is an allele?

An allele is a genetic unit that determines one of the possible forms of a gene on a given chromosome in a particular organism. Each gene can have multiple alleles, but only one can be present on a particular chromosome at a given time.

For example, a gene that determines eye color may have two alleles: an allele for blue eyes (B) and an allele for green eyes (b). If an individual has the B allele, then he will have blue eyes, and if the b allele, then he will have green eyes.

How are alleles and phenotype related?

The phenotype of an organism is determined by the combination of alleles in its genotype. Each allele can have a different expression, and the combination of these alleles can determine different phenotypes for a given gene. For example, if a person has an allele for dark hair (A) and an allele for blond hair (a), then combining them can result in a dark or blond hair phenotype.

In genetics, the terms homozygous and heterozygous are used to describe an individual's genotype. A homozygous individual has two identical alleles for a given gene, while a heterozygous individual has two different alleles.

Homozygosity and heterozygosity in the phenotype

If an organism is homozygous for a given gene (has two identical alleles), then this gene will be fully expressed. This means that an individual's phenotype will be determined only by this allele.

Allelic genes are located on identical sections of the homologous chromosome. They are the result of a mutation that occurs in one gene. Each type of organism has its own unique allelic genes. The interaction of allelic genes forms the genotype - the species designation and membership in one of the genetic groups during inbreeding. Each allelic pair of a genotype has its own specific characteristics depending on the interaction of the pair or phenotype.

The concepts of “alleles” and “genotype” are interrelated, since the second is a specification of the first. This is a set of allelic pairs. Only two forms are always connected in allelic pairs. In this case, one – the dominant one – displaces the other from the genome of the individual. What particular combination of alleles an individual will receive during pollination depends on the combination of parental genes present in the genotype of the mother and father. This happens according to Mendel's law. That is, dominant genes form, in biological terms, a dominant, and recessive genes, accordingly, a recession.

Allelic differences in gene structure can be detected by looking at chromosomes. DNA sequences, inherited sequentially in one pair and included in different parts of the chromosome, are characterized by a large number of differences. Such sequences are called iso- and hyallelic. Pleioisomeric variants containing two elements (allelic pairs) are also found.