Question

6. Mendel carried out a dihybrid cross to examine the inheritance of the characteristics for seed color and seed shape. The dominant allele for yellow seed color is Y, and the recessive allele for green color is y. The dominant allele for round seeds is R, and the recessive allele for a wrinkled shape is r. The two plants that were crossed were F1 dihybrids RrYy. Identify the ratios of traits that Mendel observed in the F2 generation. Create a Punnett square to help you answer the question.

Answer 1

Sure, I can help you with that.

To create a Punnett square for a dihybrid cross, we need to represent the possible gametes produced by each parent.

For the RrYy parent, the possible gametes are: RY, Ry, rY, ry (where R represents the dominant allele for round shape, Y represents the dominant allele for yellow color, r represents the recessive allele for wrinkled shape, and y represents the recessive allele for green color).

So the Punnett square would look like:

```
| RY | Ry | rY | ry |
--|----|----|----|----|
R | RRY| RrY| RrY| rry|
--|----|----|----|----|
r | RRy| Rry| rYr| rry|
```

Each box in the Punnett square represents a possible offspring resulting from the combination of one gamete from each parent. Now we can count the number of each genotype and phenotype among the offspring:

- Genotypic ratio: 1 RR: 2 Rr: 1 rr: 2 YY: 4 Yy: 2 yy: 4 RY: 4 rY: 4 Ry: 4 ry
- Phenotypic ratio: 9 round yellow: 3 round green: 3 wrinkled yellow: 1 wrinkled green

So in the F2 generation, Mendel observed a phenotypic ratio of 9:3:3:1 for round yellow, round green, wrinkled yellow, and wrinkled green respectively.