A cross is made between tall pea plants having green pods and dwarf pea plants having yellow pods. In the `F_(2)` generation, out of 80 plants how many are likely to be tall plants?

Options

A. 15
B. 20
C. 45
D. 60

Explanation

To solve the problem, we need to understand the genetics of the pea plants involved in the cross. Here's a step-by-step solution:

### Step 1: Identify the Traits
- **Tall (T)** is dominant over **dwarf (t)**.
- **Green pods (G)** are dominant over **yellow pods (g)**.

### Step 2: Determine the Parental Genotypes
- The tall pea plants with green pods can be either homozygous dominant (TTGG) or heterozygous (TtGg). However, since we are looking at the F2 generation, we can assume the tall parent is heterozygous (TtGg) for both traits.
- The dwarf pea plants with yellow pods must be homozygous recessive (ttgg).

### Step 3: F1 Generation
- When we cross TtGg (tall, green) with ttgg (dwarf, yellow), all F1 offspring will be TtGg (tall, green) because the tall trait is dominant.

### Step 4: F2 Generation
- To obtain the F2 generation, we need to cross two F1 plants (TtGg x TtGg).
- We can use a Punnett square to determine the genotypic and phenotypic ratios for the traits.

### Step 5: Punnett Square Analysis
- For height (T and t):
- TT (1), Tt (2), tt (1) → Ratio: 3 tall : 1 dwarf
- For pod color (G and g):
- GG (1), Gg (2), gg (1) → Ratio: 3 green : 1 yellow

### Step 6: Combine the Ratios
- The combined phenotypic ratio from the F2 generation is:
- Tall green (3/4 tall) and dwarf yellow (1/4 dwarf)
- Since the pod color does not affect the height, we focus on the height ratio.

### Step 7: Calculate the Number of Tall Plants
- Out of 80 plants in the F2 generation:
- Tall plants = 3/4 of 80 = 60

### Final Answer
Therefore, out of 80 plants in the F2 generation, **60 are likely to be tall plants**.

---