Allele
Synonyms
Allelomorph
Definition
Diploid organisms like humans carry two copies of each
autosomal chromosome (paired homologous chromosomes)
and thus, also two copies of every autosomal
gene. One of the paired chromosomes (one of the two
copies of a gene) of an individual is transmitted by the
father, the other by the mother. The sequence (order of
base pairs) of the two copies of a gene does not have to
be completely identical due to normal variation (polymorphisms)
or  mutations. Alleles are the different
(alternative, non-identical) forms of a gene or DNA
sequence at a specific genomic/chromosomal position
(locus). An individual can only possess two alleles at
each specific position on a pair of homologous chromosomes,
but a group or population may contain a lot of
different alleles at a certain locus.

Tags: , , , , , , , , , , ,