Q.Pure tall plants are crossed with pure dwarf plants. In the F1 generation, all plants were tall. These tall plants of F1 generation were selfed and the ratio of tall to dwarf plants obtained was 3:1. This is called

Step 1. Pure tall (TT) crossed with pure dwarf (tt) gives an F1 that is entirely tall (Tt) - the dwarf character is not expressed at all in F1, even though every F1 plant carries one copy of the dwarf allele.

Step 2. This total masking of one parental character by the other in F1 is exactly what dominance means: the tall allele is dominant, the dwarf allele recessive.

Step 3. Selfing the F1 lets the masked recessive allele reappear: because each Tt plant produces T and t gametes in equal numbers, self-fertilisation reconstitutes homozygous dwarf offspring (tt) alongside heterozygous and homozygous tall offspring, giving the 3 tall : 1 dwarf ratio - the standard proof that dominance is masking a trait, not erasing it. …

Recognise the F1-masks-recessive, F2-reveals-3:1 pattern as the defini …

• Choosing 'codominance' despite the F1 showing only one parental trait, not both together. …