Question

What are the possible phenotypes of the offspring from the cross on the previous page if round seeds (R) are completely dominant to wrinkled seeds (r)? What would the possible phenotypes be if round seeds were incompletely dominant to wrinkled seeds? _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________

Answer 1

To analyze the possible phenotypes of offspring from a genetic cross involving seed shape in pea plants, we need to understand two different scenarios: one where round seeds (R) are completely dominant to wrinkled seeds (r), and another where round seeds (R) are incompletely dominant to wrinkled seeds (r).

### Scenario 1: Complete Dominance

In this scenario, round seeds (R) are completely dominant over wrinkled seeds (r). The potential genotype combinations from a cross involving these alleles are:

- RR (homozygous dominant)
- Rr (heterozygous)
- rr (homozygous recessive)

When we consider the cross (e.g., RR x rr), the following phenotypes can result:

1. **If both parents are homozygous (RR x rr)**:
- All offspring (100%) will have the genotype Rr and exhibit the **round seed phenotype**.

2. **If one parent is heterozygous (Rr) and the other is homozygous recessive (rr)**:
- The offspring can be:
- 50% Rr (round seeds)
- 50% rr (wrinkled seeds)

Thus, the possible phenotypes are:
- Round seeds
- Wrinkled seeds

### Scenario 2: Incomplete Dominance

In this scenario, round seeds (R) are incompletely dominant to wrinkled seeds (r). This means that the heterozygous genotype (Rr) will produce a phenotype that is intermediate between the two homozygous forms. The phenotypes would be:

1. **If both parents are homozygous (RR x rr)**:
- All offspring (100%) will have the genotype Rr and will display the **intermediate phenotype**, which might be described as "oval" or some other distinct form that is between round and wrinkled.

2. **If one parent is heterozygous (Rr) and the other is homozygous recessive (rr)**:
- The offspring can be:
- 50% Rr (intermediate seed phenotype)
- 50% rr (wrinkled seeds)

Thus, the possible phenotypes in the case of incomplete dominance are:
- Intermediate seeds (from Rr)
- Wrinkled seeds (from rr)

### Summary of Phenotypes

1. **Complete Dominance**:
- Possible phenotypes: Round seeds, Wrinkled seeds.

2. **Incomplete Dominance**:
- Possible phenotypes: Intermediate seeds, Wrinkled seeds.