Understanding Recessive Alleles | Exploring the Basics of Gene Variation in Genetics

recessive allele

In genetics, an allele is a variant form of a gene that occurs at a specific location on a chromosome

In genetics, an allele is a variant form of a gene that occurs at a specific location on a chromosome. Alleles can be either dominant or recessive, depending on their effect on the phenotype (observable traits) of an organism.

A recessive allele is an allele that is not expressed as a phenotype when present in only one copy in an organism’s genotype. It is overridden or “masked” by the presence of a dominant allele. In other words, for a recessive trait to be expressed, an organism must inherit two copies of the recessive allele, one from each parent.

For example, let’s consider the trait for eye color. The gene responsible for eye color has multiple alleles, with brown eye color being dominant (B) and blue eye color being recessive (b). If an individual inherits the allele combination BB or Bb (one dominant allele and one recessive allele), the dominant brown eye color trait will be expressed. However, if an individual inherits the allele combination bb (two recessive alleles), the recessive blue eye color trait will be expressed.

It is worth noting that recessive alleles are not necessarily rare or less common in a population. In fact, many genetic disorders are caused by recessive alleles. Disorders such as cystic fibrosis, sickle cell anemia, and Tay-Sachs disease are caused by the presence of two copies of a recessive allele.

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