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

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:

1. The P generation and F1 generation will have all cleft chins.
2. The F1 generation will have all cleft chins.
3. 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.