Allele is described as an alternative form of a gene. There are two forms of a gene that is dominant allele ( represented by capital letter) and recessive allele ( represented by small letter).
Recessive allele does not exhibit its phenotype in presence of dominant allele. In other words, dominant allele masks the expression of recessive allele.
Example of recessive allele- 't' for dwarf height of pea plant. It is masked by dominant allele 'T' that represents tall plant height.
