A dominant allele is the variant of a gene that will produce a certain phenotype and mask the effect of any other variants of the same gene.
- The dominant allele can produce its phenotype (trait expression) even in the presence of the other form of allele .
- It is represented using capital letters .
A recessive allele is that variant of a gene that does not create a phenotype (trait expression) in the presence of a dominant allele .
- It is represented using small letters .
We know that an organism receives one copy of each gene from each parent.
There are 3 different possibilities of inheriting the gene.
Let us take the example of hair colour.
In hair colour, dark hair is the dominant trait and blonde hair is the recessive trait.
- If both parents pass alleles of dark hair to the child, the child will also have dark hair.
- If one parent passes traits of dark hair and another parent passes traits of blonde hair , even then the child will have dark hair.
- A dominant trait is always expressed even if one copy of the dominant allele is received from either of the parents
- If both parents pass the trait of blonde hair to their child, only then will the child have blonde hair.
- Recessive trait is expressed only if both copies of the gene are recessive .
Now, let us take a look at this image once again