Allele

One allele ( gr αλλήλων allélon " each other, each other" ) denotes a possible state form of a gene, which is located at a specific location ( locus) on a chromosome.

History

William Bateson took in 1902 in Mendel 's Principles of Heredity, that there are two variants of the genetic factors in each diploid cell. He called the second element allelomorph after the Greek word for " Other " and thus coined the term allele.

Importance

Due to slight variations in the base sequence of the DNA gives rise to various manifestations ( alleles) of genes. It may, for example, a gene which is responsible for the color of a flower, to give two different alleles that produce either a red or a white flower color, the plant. Accordingly, one speaks of the allele for the red or the allele for white flower color. In the gene pool of a population of more than two different state forms of a gene can occur, that is, more than two alleles occur at a locus. This is called multiple alleles. The alleles of a locus are named after the phenotype they cause. The associated wild-type allele is replaced by an additional " ".

Because people have a double set of chromosomes, each person can in its diploid cells on the two homologous chromosomes at the locus in question either two different ( " heterozygosity " ) alleles of a gene or two of the same ( " homozygous " ) possess alleles of the gene. This also applies to all other diploid organisms.

In the Japanese miracle flower, the two alleles for the expression of the flower color behave intermediately. It comes therefore to three different colored flowers: Does the plant two identical alleles for red flower color ( homozygous state), the result is a red flower. Does the plant two identical alleles for white flower color ( also homozygous state), A white flower. However, where two different alleles exist, one for the red and one for white flower color ( heterozygous state), there is a pink flower ( intermediate mode of inheritance ).

Usually dominates an allele in the heterozygous state over the other. Allele that determines the value of the characteristic in the phenotype is dominant called while the other allele is called recessive.

From co-dominance occurs when two different alleles of equal importance to determine the expression of a characteristic.