What is the Difference Between Dominant and Recessive Alleles?

The difference between dominant and recessive alleles lies in their interaction and expression in an organism. Here are the key differences:

1. Expression: A dominant allele shows its effect even if the individual has only one copy of the allele, while a recessive allele only shows its effect if the individual has two copies of the allele.
2. Inheritance: For a dominant allele to be expressed, only one copy of the allele is needed, which can come from either parent. In contrast, for a recessive allele to be expressed, the individual must have two copies, one from each parent.
3. Dominance Relationship: An allele is considered dominant when it effectively overrules the other recessive allele. For example, the allele for brown eyes (B) is dominant over the allele for blue eyes (b). If an individual has one allele for brown eyes and one allele for blue eyes (Bb), their eyes will be brown.
4. Notation: Dominant alleles are denoted by a capital letter, while recessive alleles are denoted by a small letter.

Some examples of dominant and recessive traits include eye color and blood groups. The allele for brown eyes (B) is dominant over the allele for blue eyes (b), so if a person has one allele for brown eyes and one for blue eyes, their eyes will be brown. In the case of blood groups, the A and B alleles are co-dominant, meaning they are both equally ‘strong’ and produce a combined physical trait when present together.

Comparative Table: Dominant vs Recessive Alleles

The difference between dominant and recessive alleles can be summarized in the following table:

For example, the allele for brown eyes is dominant, so you only need one copy of the 'brown eye' allele to have brown eyes. On the other hand, the allele for blue eyes is recessive, so you need two copies of the 'blue eye' allele to have blue eyes.