Alleelien

Alleelien is not a standard term in English genetics. In some Dutch-language sources, alleelien may be used as a plural form of alleel, equivalent to the English plural allele. The more common Dutch plural is allelen, and in English the standard term is allele with plural alleles. The exact usage can vary by language and source.

An allele is one of the alternative forms of a gene at a given locus. Most individuals carry two alleles for each gene, one inherited from each parent, though some genes exist in more complex copy-number forms in certain contexts. Alleles can be identical (homozygous) or different (heterozygous). They influence phenotype when they affect the gene product or its regulation. Alleles arise by mutation and are shaped by evolutionary forces such as natural selection, genetic drift, migration, and further mutation.

In population genetics, allele frequencies describe how common an allele is within a population. For two alleles A and a with frequencies p and q (where p + q = 1), the Hardy-Weinberg principle predicts genotype frequencies of p^2, 2pq, and q^2 for AA, Aa, and aa in an idealized large, randomly mating population without evolutionary forces.

Allelic variation underpins Mendelian inheritance, genetic diversity, and many traits. Allele information is applied across fields including medicine, agriculture, forensics, and evolutionary biology. While the term alleelien may appear in some language contexts, the foundational concept remains the allele and its role in heredity and variation.