Understanding Dominant Alleles and Their Effect on Phenotype

An allele whose trait always shows up in the organism when the allele is present

The allele you are describing is called a dominant allele

The allele you are describing is called a dominant allele. Dominant alleles are represented by uppercase letters, while recessive alleles are represented by lowercase letters. When an organism has at least one copy of a dominant allele, the trait associated with that allele will be expressed or shown in its phenotype, which is the physical appearance of the trait.

For example, let’s consider the trait for tongue rolling. The ability to roll one’s tongue is determined by a gene with two possible alleles – one for tongue rolling (T) and one for non-tongue rolling (t). The dominant allele (T) for tongue rolling always shows up in the organism when present, and the recessive allele (t) does not show up if there is at least one dominant allele.

Therefore, if an individual has at least one copy of the dominant allele (T), they will exhibit the phenotype of being able to roll their tongue. It doesn’t matter whether the individual has one or two copies of the dominant allele; the trait will always be expressed. On the other hand, individuals who are homozygous for the recessive allele (tt) will not be able to roll their tongue, as the recessive allele does not cause the trait to be expressed.

This example illustrates the concept of dominance, where the presence of a dominant allele overrides the presence of the recessive allele and determines the phenotype of the organism.

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