Monohybrid cross worksheet with completed Punnett squares and handwritten answers for genetics problems.

Problem Analysis and Solution

The task involves completing monohybrid crosses using Punnett squares. A Punnett square is a graphical tool used to predict the genotype and phenotype of offspring from a genetic cross. The key points to remember are:
1. Capital letters represent dominant alleles.
2. Lowercase letters represent recessive alleles.
3. The phenotype is determined by the genotype based on dominance/recessiveness.

Let's solve each problem step by step.

---

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

#### Step 1: Identify the genotypes
- Parent 1: Gg (heterozygous green)
- Parent 2: gg (homozygous yellow)

#### Step 2: Set up the Punnett square
- Parent 1 contributes alleles: G or g
- Parent 2 contributes alleles: g

Punnett square:
```
g g
G Gg Gg
g gg gg
```

#### Step 3: Determine the genotypes and phenotypes
- Genotypes:
- Gg (heterozygous green): 2
- gg (homozygous yellow): 2
- Ratio: 2 Gg : 2 gg

- Phenotypes:
- Green (G_): 2 (Gg)
- Yellow (gg): 2
- Ratio: 2 green : 2 yellow

#### Final Answer:
```
Genotype: 2 Gg : 2 gg
Phenotype: 2 green : 2 yellow
```

---

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

#### Step 1: Identify the genotypes
- Parent 1: TT (homozygous tall)
- Parent 2: Tt (heterozygous tall)

#### Step 2: Set up the Punnett square
- Parent 1 contributes alleles: T
- Parent 2 contributes alleles: T or t

Punnett square:
```
T t
T TT Tt
T TT Tt
```

#### Step 3: Determine the genotypes and phenotypes
- Genotypes:
- TT (homozygous tall): 2
- Tt (heterozygous tall): 2
- Ratio: 2 TT : 2 Tt

- Phenotypes:
- Tall (T_): 4 (all TT and Tt)
- Short (tt): 0
- Ratio: 4 tall : 0 short

#### Final Answer:
```
Genotype: 2 TT : 2 Tt
Phenotype: 4 tall : 0 short
```

---

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

#### Step 1: Identify the genotypes
- Parent 1: Tt (heterozygous tall)
- Parent 2: tt (homozygous short)

#### Step 2: Set up the Punnett square
- Parent 1 contributes alleles: T or t
- Parent 2 contributes alleles: t

Punnett square:
```
t t
T Tt Tt
t tt tt
```

#### Step 3: Determine the genotypes and phenotypes
- Genotypes:
- Tt (heterozygous tall): 2
- tt (homozygous short): 2
- Ratio: 2 Tt : 2 tt

- Phenotypes:
- Tall (T_): 2 (Tt)
- Short (tt): 2
- Ratio: 2 tall : 2 short

#### Final Answer:
```
Genotype: 2 Tt : 2 tt
Phenotype: 2 tall : 2 short
```

---

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

#### Step 1: Identify the genotypes
- Parent 1: RR (homozygous red)
- Parent 2: rr (homozygous white)

#### Step 2: Set up the Punnett square
- Parent 1 contributes alleles: R
- Parent 2 contributes alleles: r

Punnett square:
```
r r
R Rr Rr
R Rr Rr
```

#### Step 3: Determine the genotypes and phenotypes
- Genotypes:
- Rr (heterozygous red): 4
- Ratio: 4 Rr

- Phenotypes:
- Red (R_): 4 (all Rr)
- White (rr): 0
- Ratio: 4 red : 0 white

#### Final Answer:
```
Genotype: 4 Rr
Phenotype: 4 red : 0 white
```

---

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

#### Step 1: Identify the genotypes
- Parent 1: rr (homozygous white)
- Parent 2: rr (homozygous white)

#### Step 2: Set up the Punnett square
- Parent 1 contributes alleles: r
- Parent 2 contributes alleles: r

Punnett square:
```
r r
r rr rr
r rr rr
```

#### Step 3: Determine the genotypes and phenotypes
- Genotypes:
- rr (homozygous white): 4
- Ratio: 4 rr

- Phenotypes:
- White (rr): 4
- Red (R_): 0
- Ratio: 4 white : 0 red

#### Final Answer:
```
Genotype: 4 rr
Phenotype: 4 white : 0 red
```

---

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

#### Step 1: Identify the genotypes
- Parent 1: BB (homozygous black)
- Parent 2: Bb (heterozygous black)

#### Step 2: Set up the Punnett square
- Parent 1 contributes alleles: B
- Parent 2 contributes alleles: B or b

Punnett square:
```
B b
B BB Bb
B BB Bb
```

#### Step 3: Determine the genotypes and phenotypes
- Genotypes:
- BB (homozygous black): 2
- Bb (heterozygous black): 2
- Ratio: 2 BB : 2 Bb

- Phenotypes:
- Black (B_): 4 (all BB and Bb)
- Non-black (bb): 0
- Ratio: 4 black : 0 non-black

#### Final Answer:
```
Genotype: 2 BB : 2 Bb
Phenotype: 4 black : 0 non-black
```

---

Final Summary of All Answers

1. Green pea (Gg) × Yellow pea (gg):
- Genotype: 2 Gg : 2 gg
- Phenotype: 2 green : 2 yellow

2. Tall plant (TT) × Tall plant (Tt):
- Genotype: 2 TT : 2 Tt
- Phenotype: 4 tall : 0 short

3. Tall plant (Tt) × Short plant (tt):
- Genotype: 2 Tt : 2 tt
- Phenotype: 2 tall : 2 short

4. Red flower (RR) × White flower (rr):
- Genotype: 4 Rr
- Phenotype: 4 red : 0 white

5. White flower (rr) × White flower (rr):
- Genotype: 4 rr
- Phenotype: 4 white : 0 red

6. Black chicken (BB) × Black chicken (Bb):
- Genotype: 2 BB : 2 Bb
- Phenotype: 4 black : 0 non-black

---

Final Boxed Answers:
\[
\boxed{
\begin{array}{l}
1. \text{Genotype: } 2 \text{ Gg : } 2 \text{ gg, Phenotype: } 2 \text{ green : } 2 \text{ yellow} \\
2. \text{Genotype: } 2 \text{ TT : } 2 \text{ Tt, Phenotype: } 4 \text{ tall : } 0 \text{ short} \\
3. \text{Genotype: } 2 \text{ Tt : } 2 \text{ tt, Phenotype: } 2 \text{ tall : } 2 \text{ short} \\
4. \text{Genotype: } 4 \text{ Rr, Phenotype: } 4 \text{ red : } 0 \text{ white} \\
5. \text{Genotype: } 4 \text{ rr, Phenotype: } 4 \text{ white : } 0 \text{ red} \\
6. \text{Genotype: } 2 \text{ BB : } 2 \text{ Bb, Phenotype: } 4 \text{ black : } 0 \text{ non-black}
\end{array}
}
\]