To determine the generations based on Mendel's method of crossing true-breeding parents with opposite traits, let's define the genetic makeup for cleft chin and no-cleft chin:
- Let "C" represent the dominant allele for a cleft chin.
- Let "c" represent the recessive allele for a no-cleft chin.
P Generation: If we start with a true-breeding cleft chin parent (CC) and a true-breeding no-cleft chin parent (cc), their genotypes are:
- Parent 1 (cleft chin): CC
- Parent 2 (no-cleft chin): cc
F1 Generation: When these two are crossed, all offspring (F1 generation) will inherit one allele from each parent:
- All offspring will be heterozygous (Cc) and will express the dominant trait (cleft chin).
So, the F1 generation will have all cleft chins.
F2 Generation: If we now cross two individuals from the F1 generation (Cc x Cc), we can use a Punnett square to determine the genotypes of the F2 generation:
\[ \begin{array}{c|c|c} & C & c \ \hline C & CC & Cc \ \hline c & Cc & cc \ \end{array} \]
From this square, the genotypes of the F2 generation will be:
- 1 CC (cleft chin)
- 2 Cc (cleft chin)
- 1 cc (no-cleft chin)
This means the F2 generation will have:
- 3 cleft chin individuals (CC and Cc)
- 1 no-cleft chin individual (cc)
Conclusion: Based on this genetic analysis, the correct conclusions drawn from your options are:
- 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 cleft chins and no-cleft chins.
Thus, the following statements are correct:
- 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 cleft chins and no-cleft chins.