Monohybrid Cross Practice Problems Using Punnett Squares

Problem Analysis

The task involves completing Punnett squares for monohybrid crosses and determining the genotypic and phenotypic ratios of the offspring. The instructions specify that capital letters represent dominant alleles, and lowercase letters represent recessive alleles.

Solution Explanation

#### 1. A green pea plant (Gg) is crossed with a yellow pea plant (gg)

- Punnett Square:
```
G g
g GG Gg
g Gg gg
```

- Genotypes:
- GG: 1
- Gg: 2
- gg: 1

- Phenotypes:
- Green (G_): 3 (GG, Gg)
- Yellow (gg): 1

- Ratio:
- Genotype: 1 GG : 2 Gg : 1 gg
- Phenotype: 3 Green : 1 Yellow

---

#### 2. A tall plant (TT) is crossed with a tall plant (Tt)

- Punnett Square:
```
T t
T TT Tt
T TT Tt
```

- Genotypes:
- TT: 2
- Tt: 2

- Phenotypes:
- Tall (T_): 4 (TT, Tt)

- Ratio:
- Genotype: 2 TT : 2 Tt
- Phenotype: 4 Tall : 0 Short

---

#### 3. A tall plant (Tt) is crossed with a short plant (tt)

- Punnett Square:
```
T t
t Tt tt
t Tt tt
```

- Genotypes:
- Tt: 2
- tt: 2

- Phenotypes:
- Tall (Tt): 2
- Short (tt): 2

- Ratio:
- Genotype: 2 Tt : 2 tt
- Phenotype: 2 Tall : 2 Short

---

#### 4. A red flower (Rr) is crossed with a white flower (rr)

- Punnett Square:
```
R r
r Rr rr
r Rr rr
```

- Genotypes:
- Rr: 2
- rr: 2

- Phenotypes:
- Red (Rr): 2
- White (rr): 2

- Ratio:
- Genotype: 2 Rr : 2 rr
- Phenotype: 2 Red : 2 White

---

#### 5. A white flower (rr) is crossed with a white flower (rr)

- Punnett Square:
```
r r
r rr rr
r rr rr
```

- Genotypes:
- rr: 4

- Phenotypes:
- White (rr): 4

- Ratio:
- Genotype: 4 rr
- Phenotype: 4 White

---

#### 6. A black chicken (BB) is crossed with a black chicken (BB)

- Punnett Square:
```
B B
B BB BB
B BB BB
```

- Genotypes:
- BB: 4

- Phenotypes:
- Black (BB): 4

- Ratio:
- Genotype: 4 BB
- Phenotype: 4 Black

---

Final Answers

1. Genotype Ratio: 1 GG : 2 Gg : 1 gg
Phenotype Ratio: 3 Green : 1 Yellow

2. Genotype Ratio: 2 TT : 2 Tt
Phenotype Ratio: 4 Tall : 0 Short

3. Genotype Ratio: 2 Tt : 2 tt
Phenotype Ratio: 2 Tall : 2 Short

4. Genotype Ratio: 2 Rr : 2 rr
Phenotype Ratio: 2 Red : 2 White

5. Genotype Ratio: 4 rr
Phenotype Ratio: 4 White

6. Genotype Ratio: 4 BB
Phenotype Ratio: 4 Black

Final Answer:
\boxed{
\begin{array}{l}
1. \text{Genotype: } 1 GG : 2 Gg : 1 gg, \text{ Phenotype: } 3 \text{ Green} : 1 \text{ Yellow} \\
2. \text{Genotype: } 2 TT : 2 Tt, \text{ Phenotype: } 4 \text{ Tall} : 0 \text{ Short} \\
3. \text{Genotype: } 2 Tt : 2 tt, \text{ Phenotype: } 2 \text{ Tall} : 2 \text{ Short} \\
4. \text{Genotype: } 2 Rr : 2 rr, \text{ Phenotype: } 2 \text{ Red} : 2 \text{ White} \\
5. \text{Genotype: } 4 rr, \text{ Phenotype: } 4 \text{ White} \\
6. \text{Genotype: } 4 BB, \text{ Phenotype: } 4 \text{ Black} \\
\end{array}
}