Answer :
To solve this problem and determine the expected ratio of red- to white-flowering plants in the F2 generation, we analyze the genetic cross using a Punnett square.
1. Understand the Traits and Alleles:
- The red flower trait is determined by the presence of the dominant allele, R. This can be seen in genotypes RR or Rr.
- The white flower trait is determined by the presence of the recessive allele, r, which is expressed only in the genotype rr.
2. Set Up the Cross:
- The horticulturalist crosses two geraniums from the F1 generation. If we assume the F1 generation is all heterozygous (Rr), each parent can produce gametes with either R or r.
3. Create the Punnett Square:
- Each parent (Rr) contributes either R or r. We draw a 2x2 grid to simulate the cross.
```
| | R | r |
|-----|-----|-----|
| R | RR | Rr |
| r | Rr | rr |
```
4. Determine Genotypes of Offspring:
- The possible combinations are:
- RR
- Rr (from both second row, first column and first row, second column)
- rr
5. Determine Phenotypes:
- Genotypes RR and Rr both result in red flowers.
- Genotype rr results in white flowers.
6. Count the Phenotypes:
- Red-flowering plants: RR, Rr, Rr (3 possibilities)
- White-flowering plants: rr (1 possibility)
7. Calculate the Ratio:
- The phenotypic ratio of red to white flowers is 3:1.
Therefore, the expected ratio of red- to white-flowering plants in the F2 generation is 3:1.
1. Understand the Traits and Alleles:
- The red flower trait is determined by the presence of the dominant allele, R. This can be seen in genotypes RR or Rr.
- The white flower trait is determined by the presence of the recessive allele, r, which is expressed only in the genotype rr.
2. Set Up the Cross:
- The horticulturalist crosses two geraniums from the F1 generation. If we assume the F1 generation is all heterozygous (Rr), each parent can produce gametes with either R or r.
3. Create the Punnett Square:
- Each parent (Rr) contributes either R or r. We draw a 2x2 grid to simulate the cross.
```
| | R | r |
|-----|-----|-----|
| R | RR | Rr |
| r | Rr | rr |
```
4. Determine Genotypes of Offspring:
- The possible combinations are:
- RR
- Rr (from both second row, first column and first row, second column)
- rr
5. Determine Phenotypes:
- Genotypes RR and Rr both result in red flowers.
- Genotype rr results in white flowers.
6. Count the Phenotypes:
- Red-flowering plants: RR, Rr, Rr (3 possibilities)
- White-flowering plants: rr (1 possibility)
7. Calculate the Ratio:
- The phenotypic ratio of red to white flowers is 3:1.
Therefore, the expected ratio of red- to white-flowering plants in the F2 generation is 3:1.
