How many phenotyes w.r.t. flower colour are possible if heterozygous Lathyrus odoratus for two loci is selfed ?

Options

A. 3
B. 1
C. 4
D. 2

Answer

To determine how many phenotypes with respect to flower color are possible when heterozygous Lathyrus odoratus (sweet pea) is selfed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Genotype**:
- Lathyrus odoratus has two flower colors: purple and white.
- Let’s denote purple with "P" (dominant) and white with "c" (recessive).
- A heterozygous individual for flower color would be represented as "PpCc".

2. **Identifying the Alleles**:
- Since we are dealing with two loci (P and C), each locus can have two alleles.
- The alleles for the flower color are:
- For locus P: P (purple) and p (white)
- For locus C: C (purple) and c (white)

3. **Setting Up the Cross**:
- When we self a heterozygous individual (PpCc x PpCc), we can use a Punnett square to determine the possible combinations of alleles in the offspring.

4. **Creating the Punnett Square**:
- For each locus, the gametes produced by the parents will be:
- From Pp: P, p
- From Cc: C, c
- The possible gametes from one parent are: PC, Pc, pC, pc.
- The same gametes will be produced by the other parent.

5. **Calculating the Offspring Combinations**:
- By combining the gametes from both parents in a 4x4 Punnett square, we can determine the genotypes of the offspring:
- PC, PC
- PC, Pc
- pC, PC
- pC, Pc
- PC, pc
- Pc, pc
- pC, pc
- pc, pc

6. **Determining the Phenotypes**:
- The phenotypes are determined by the presence of at least one dominant allele for each color:
- Purple flowers will appear if at least one P and one C are present.
- White flowers will appear if there are no dominant alleles present.
- The resulting phenotypes from the combinations will be:
- Purple (P_C)
- White (ppcc)

7. **Final Count of Phenotypes**:
- After analyzing the combinations, we find that there are only two distinct phenotypes: purple and white.

### Conclusion:
Thus, the total number of phenotypes with respect to flower color possible when heterozygous Lathyrus odoratus is selfed is **2**.