Dictionary » A » Allele



noun, plural: alleles


One member of a pair (or any of the series) of genes occupying a specific spot on a chromosome (called locus) that controls the same trait.


For example, a pair of alleles controlling the same trait, i.e. eye color: one allele codes for blue eyes, another allele for brown eyes.

In humans, simple traits such as eye color may be caused by the interaction of only one pair of alleles. But for complex traits, such as height, they are usually caused by the interactions of series of alleles. Some alleles are dominant over other alleles, as in the case of heterozygous pairings (where paired alleles are different, in contrast to homozygous pairings where alleles are the same). In the above example, since the alleles code for different eye colors they are heterozygous.

Colloquially, the term gene is used when referring to an inherited trait that is usually accompanied by a phenotype as in ‘tall genes’ or ‘bad genes’ – but the more proper (scientific) term for this is allele.

Word origin: From German Allel, shortened from Allelomorph, from English allelomorph.
Related forms: allelic (adjective), biallelic (adjective), diallelic (adjective), monoallelic (adjective), allelism (noun), nonallelic (adjective).
Synonym: allelomorph.
See also: gene, trait, loci, DNA, chromosome.

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Microevolution verus Macroevolution

Evolution is defined as variation in the frequencies of alleles, where an allele is a specific iteration of a given gene. Microevolution is defined as variations in the frequencies of alleles below species level, in a population of organisms. Macroevolution ...

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by hackenslash
Thu Mar 06, 2014 8:57 am
Forum: Evolution
Topic: Microevolution verus Macroevolution
Replies: 15
Views: 17627

Blood Genetics help please

The A, B and O antigens of the human blood system are sugars that can be found on the surface of red blood cells. The alleles A, B and O refer to the variant forms of the proteins (enzymes) that produce the sugar antigens. The O allele enzyme is non-functional, so that the basic sugar ...

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by girlslovebarbie
Sat Feb 01, 2014 2:58 pm
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Topic: Blood Genetics help please
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Pedigree Analysis Question

... they will produce a child which is affected. How do I do so? 3) I am then asked to calculate the probability that either A or B have a recessive allele. 4) Finally, I need to find the probability that A&B will produce a child that has a recessive allele. Thanks very much! Any help is appreciated!

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by ApothemCyte
Sat Jan 18, 2014 8:44 pm
Forum: Genetics
Topic: Pedigree Analysis Question
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Views: 366

Need some help segregation - independent assortment!!!

All diploid organisms have a pair of alleles for a particular trait. These alleles are present on homologous chromosomes. Segregation means that these alleles are separated during gamete formation and there is only one allele in a gamete, not ...

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by supersapien
Fri Nov 29, 2013 2:36 am
Forum: Genetics
Topic: Need some help segregation - independent assortment!!!
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I Need Help understanding gametes, genotypes and phenotypes

... doing more work than it is asking you to do. Post Two: lowercase i is recessive and uppercase I is dominant, but there are actually two codominant alleles. I^A is dominant allele for type A, and I^B is dominant allele for type B. There is only an exception if the have the Bombay phenotype, which ...

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by wildfunguy
Tue Oct 29, 2013 3:25 pm
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Topic: I Need Help understanding gametes, genotypes and phenotypes
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