In corn, the trait for tall plants (T) is dominant to the trait for dwarf plant (t) and the trait for coloured kernels (C) is dominant to the trait for white kernels (c). In a particular cross of corn plant, the probability of an offspring being tall is 0.5 and probability of a kernel being coloured in 0.75. Which of the following most probabily represents the parental genotypes ?

Options

A. TtCc`X `TtCc
B. TtCc `X` ttCc
C. TtCc `X` ttcc
D. TTCc `X` ttCc

Answer

To solve the problem, we need to determine the parental genotypes based on the probabilities of the offspring being tall and having colored kernels.

### Step-by-Step Solution:

1. **Identify the Traits and Their Dominance**:
- Tall plants (T) are dominant over dwarf plants (t).
- Colored kernels (C) are dominant over white kernels (c).

2. **Understand the Given Probabilities**:
- Probability of offspring being tall = 0.5 (50%).
- Probability of offspring having colored kernels = 0.75 (75%).

3. **Set Up the Dihybrid Cross**:
- Since we are dealing with two traits, we will perform a dihybrid cross.
- The parental genotypes must be such that they can produce the given probabilities.

4. **Determine Possible Parental Genotypes**:
- The offspring being 50% tall suggests that one parent must be heterozygous (Tt) and the other could be either homozygous recessive (tt) or heterozygous (Tt).
- The offspring being 75% colored kernels suggests that at least one parent must be heterozygous (Cc) and the other could be homozygous recessive (cc) or heterozygous (Cc).

5. **Choose the Likely Parental Genotypes**:
- Let's consider the combination: TtCc (heterozygous tall and colored) x ttCc (dwarf and heterozygous colored).
- This combination will allow us to calculate the offspring ratios.

6. **Perform the Punnett Square**:
- For TtCc x ttCc:
- Gametes from TtCc: TC, Tc, tC, tc
- Gametes from ttCc: tC, tc
- The Punnett square will yield the following combinations:
- TC (Tall, Colored)
- Tc (Tall, Colored)
- tC (Dwarf, Colored)
- tc (Dwarf, White)
- Resulting offspring:
- 2 Tall, Colored (TC, Tc)
- 1 Tall, White (Tc)
- 2 Dwarf, Colored (tC)
- 1 Dwarf, White (tc)

7. **Calculate the Ratios**:
- Total offspring = 8
- Tall plants = 4 (2 Tall, Colored + 2 Tall, White) = 50%
- Colored kernels = 6 (2 Tall, Colored + 4 Dwarf, Colored) = 75%

8. **Conclusion**:
- The parental genotypes that most likely represent the given probabilities are TtCc (tall, colored) and ttCc (dwarf, colored).

### Final Answer:
The most probable parental genotypes are TtCc (tall, colored) and ttCc (dwarf, colored).