Question

In humans, a cleft chin is dominant and no-cleft is recessive. What will the generations look like? Assume that Mendel’s method of crossing two true breeding parents with opposite traits is followed. Check all that apply. The P generation, F1 generation, and F2 generation will have all cleft chins. The P generation, F1 generation, and F2 generation will have all no-cleft chins. The P generation and F1 generation will have all cleft chins. The F1 generation will have all cleft chins. The P generation and F2 generation will have all no-cleft chins. The P generation and F2 generation will have cleft chins and no-cleft chins. The P generation, F1 generation, and F2 generation will have cleft chins and no-cleft chins.

Answer 1

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.

Answer 2

The answer is:

The F1 generation will have all cleft chin. 
The P generation and F2 generation will have cleft chins and no-cleft chin.