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A recessive allele is a variety of genetic code that does not create a phenotype if a dominant allele is present. In a dominant/recessive relationship between two alleles, the recessive allele’s effects are masked by the more dramatic effects of the dominant allele.
Individuals inherit two versions of each gene, known as alleles, from each parent. In the case of a recessive trait, the alleles of the trait-causing gene are the same, and both (recessive) alleles must be present to express the trait.
People with light eyes tend to carry recessive alleles of the major genes; people with dark eyes tend to carry dominant alleles. In Scandinavia, most people have light eyes—the recessive alleles of these genes are much more common here than the dominant ones.
If an allele is recessive, then the gene needs to have two copies (or be homozygous) to express the recessive phenotype. If an organism is a heterozygote, or has one copy of each allele type, then it will show the dominant phenotype.
Recessive alleles only show their effect if the individual inherits two copies of the allele – one from each parent. If an individual has only one copy of the recessive allele, they are generally considered to be a ‘carrier’ of the recessive allele.
Alleles determine whether a phenotype, or physical trait, is dominant or recessive. A dominant allele is expressed even if only one copy is present, while a recessive allele requires two copies (homozygous) for expression.
Recessive alleles often lead to reduced function or loss of function. Albinism, for example, is an inherited condition in which the body produces very little melanin. Melanin is a molecule that provides pigment in skin, hair and eyes. Advertisement.
A recessive gene is a gene whose effects are masked in the presence of a dominant gene. Every organism that has DNA packed into chromosomes has two alleles, or forms of a gene, for each gene: one inherited from their mother, and one inherited from their father.
Some alleles are dominant or recessive. When an organism is heterozygous at a specific locus and carries one dominant and one recessive allele, the organism will express the dominant phenotype.
Recessive alleles express their trait only when there is no dominant allele present. Blue eye alleles are recessive, so if you have both the brown and blue eye alleles, you will still have brown eyes.