Let's analyze the problem step by step.
1. P Generation:
- We start with two true-breeding parents with opposite traits.
- Let [tex]\( C \)[/tex] represent the dominant allele for cleft chin and [tex]\( c \)[/tex] represent the recessive allele for no-cleft chin.
- One parent is homozygous dominant ([tex]\( CC \)[/tex]) and the other is homozygous recessive ([tex]\( cc \)[/tex]).
- When crossed ([tex]\( CC \times cc \)[/tex]), all offspring (F1 generation) will be heterozygous ([tex]\( Cc \)[/tex]) and will display the dominant trait (cleft chin).
2. F1 Generation:
- All offspring from the P generation cross are [tex]\( Cc \)[/tex], expressing cleft chins.
- When two [tex]\( Cc \)[/tex] individuals are crossed ([tex]\( Cc \times Cc \)[/tex]), the F2 generation will have a combination of genotypes.
3. F2 Generation:
- The offspring from the [tex]\( Cc \times Cc \)[/tex] cross can have the following genotypes:
- [tex]\( CC \)[/tex] (homozygous dominant)
- [tex]\( Cc \)[/tex] (heterozygous)
- [tex]\( cc \)[/tex] (homozygous recessive)
- The phenotypic ratio will be:
- 1 [tex]\( CC \)[/tex] (cleft chin)
- 2 [tex]\( Cc \)[/tex] (cleft chin)
- 1 [tex]\( cc \)[/tex] (no-cleft chin)
- This results in 3 offspring with cleft chins and 1 with no-cleft chin.
Based on this analysis:
- The [tex]\( P \)[/tex] generation has all cleft chins.
- The [tex]\( F1 \)[/tex] generation has all cleft chins.
- The [tex]\( F2 \)[/tex] generation has both cleft chins and no-cleft chins. Specifically, there will be a 3:1 phenotypic ratio of cleft chin to no-cleft chin.
Given these observations, the correct options are:
- The [tex]\( P \)[/tex] generation and [tex]\( F1 \)[/tex] generation will have all cleft chins.
- The [tex]\( F2 \)[/tex] generation will have both cleft chins and no-cleft chins.
These correlate to the following statements:
- The [tex]\( P \)[/tex] generation and [tex]\( F1 \)[/tex] generation will have all cleft chins.
- The [tex]\( F2 \)[/tex] generation will have cleft chins and no-cleft chins.
Therefore, the correct statements to check are:
- The [tex]\( P \)[/tex] generation and [tex]\( F1 \)[/tex] generation will have all cleft chins.
- The [tex]\( F2 \)[/tex] generation will have cleft chins and no-cleft chins.
Thus, our corresponding options are:
1. The P generation, F1 generation, and F2 generation will have all cleft chins. (Incorrect)
2. The P generation, F1 generation, and F2 generation will have all no-cleft chins. (Incorrect)
3. The P generation and F1 generation will have all cleft chins. (Correct)
4. The F1 generation will have all cleft chins. (Correct but incomplete)
5. The P generation and F2 generation will have all no-cleft chins. (Incorrect)
6. The P generation and F2 generation will have cleft chins and no-cleft chins. (Incorrect)
7. The P generation, F1 generation, and F2 generation will have cleft chins and no-cleft chins. (Incorrect)
So only statements 3 and 6 are correct:
- The P generation and F1 generation will have all cleft chins. (Corresponds to 2 in numerical result)
- The F2 generation will have cleft chins and no-cleft chins. (Corresponds to 6 in numerical result)
