Answer:
The P generation and F1 generation will have all cleft chins.
The F1 generation will have all cleft chins.
Explanation:
In humans, if a cleft chin is dominant and no cleft chin is recessive and two true breeding parents are crossed then P and F1 generation will have all cleft chins while F2 generation will have 75% progenies with cleft chins and 25% with no cleft chin.
Let us consider 'A' represents dominant trait (cleft chin) & 'a' represents recessive trait (no cleft chin). The cross is shown as under:
Parental AA x aa
F1 generation Aa Aa Aa Aa
Now for F2 generation, F1 generation progenies which are heterozygotes i.e. Aa & Aa will mate.
F1 generation Aa x Aa
F2 generation AA Aa Aa aa
Although, progenies in F1 generation are heterozygotes for the trait yet phenotypically they all will be born with cleft chin.