codominance allele - Often, one allele in the pair expresses itself more than the other. A dominant allele masks the effect of other alleles for the trait. For example, if a person has one allele for free earlobes and one allele for attached earlobes, that person has a phenotype of free earlobes. We say the allele for free earlobes is dominant. A recessive allele is one that, when present with another allele, has its actions overshadowed by the other; it is masked by the effect of the other allele.
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| Codominance Allele |
Having attached earlobes is the result of having a combination of two recessive characteristics. A person with one allele for free earlobes and one allele for attached earlobes has a phenotype of free earlobes. The expression of recessive alleles is only noted when the organism is homozygous for the recessive alleles. If you have attached earlobes, you have two alleles for that trait. Don’t think that recessive alleles are necessarily bad. The term recessive has nothing to do with the significance or value of the allele—it simply describes how it can be expressed. Recessive alleles are not less likely to be inherited but must be present in a homozygous condition to express themselves. Also, recessive alleles are not necessarily less frequent in the population.
Sometimes the physical environment determines whether or not dominant or recessive genes function. For example, in humans genes for freckles do not show themselves fully unless a person’s skin is exposed to sunlight
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