We know that two alleles (one from each parent) are passed on to the child.
If both the alleles are identical , they are called Homozygous alleles
- Homo → same
- Zygous → having genetic material.
If the two alleles are dissimilar , they are called Heterozygous alleles .
- Hetero → different
- Zygous → having genetic material.
For example -
Let us consider the pod colour of pea plant.
- The two alleles produced are Green colour pods and Yellow colour pods .
- Green colour pods is the dominant trait and yellow colour pods is the recessive trait.
- So we will assign ‘G’ for the green pod and ‘g’ for the yellow pod .
1. HOMOZYGOUS DOMINANT
- If both the alleles are Dominant , the plant will have Homozygous Dominant alleles.
- Phenotype: Green colour pods
- Genotype: GG
2. HOMOZYGOUS RECESSIVE
- If both the alleles are Recessive , the plant will have Homozygous Recessive alleles.
- Phenotype: Yellow colour pods
- Genotype: gg
3. HETEROZYGOUS DOMINANT
- If one allele is Dominant and other allele is recessive, the plant has Heterozygous Dominant alleles.
- Phenotype: Green colour pods
- Genotype: Gg
NOTE - Remember, the dominant allele can produce its phenotype (trait expression) even in the presence of the other form of allele .
Hence the heterozygous pair of alleles is called heterozygous dominant condition .
