Genetics Practice - Punnett Square Worksheet with Answer Key.

It looks like you've uploaded a genetics worksheet titled "Genetics Practice - Punnett Square KEY", which includes several problems involving Punnett squares for traits such as pea plant color, shape, and height, using Mendelian genetics principles.

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Problem 1: Pea Plant Color – Green vs Yellow

Trait: Seed color
- G = green (dominant)
- g = yellow (recessive)

#### Cross: Gg x Gg

| | G | g |
|-------|-------|-------|
| G | GG | Gg |
| g | Gg | gg |

Phenotypes:
- Green: GG, Gg → 3/4
- Yellow: gg → 1/4

Answer:
- Genotypic ratio: 1 GG : 2 Gg : 1 gg
- Phenotypic ratio: 3 green : 1 yellow

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Problem 2: Pea Plant Shape – Round vs Wrinkled

Trait: Seed shape
- R = round (dominant)
- r = wrinkled (recessive)

#### Cross: Rr x Rr

| | R | r |
|-------|-------|-------|
| R | RR | Rr |
| r | Rr | rr |

Phenotypes:
- Round: RR, Rr → 3/4
- Wrinkled: rr → 1/4

Answer:
- Genotypic ratio: 1 RR : 2 Rr : 1 rr
- Phenotypic ratio: 3 round : 1 wrinkled

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Problem 3: Cross between Homozygous Dominant and Heterozygous

#### Cross: GG x Gg

| | G | g |
|-------|-------|-------|
| G | GG | Gg |
| G | GG | Gg |

Genotypes:
- GG: 2/4 = 1/2
- Gg: 2/4 = 1/2

Phenotypes:
- All offspring are green (since G is dominant)

Answer:
- Genotypic ratio: 1 GG : 1 Gg
- Phenotypic ratio: All green (100%)
- Number of offspring with green phenotype: 4 out of 4
- Number with yellow: 0

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Problem 4: Cross between Homozygous Recessive and Heterozygous

#### Cross: rr x Rr

| | R | r |
|-------|-------|-------|
| r | Rr | rr |
| r | Rr | rr |

Genotypes:
- Rr: 2/4 = 1/2
- rr: 2/4 = 1/2

Phenotypes:
- Round: Rr → 1/2
- Wrinkled: rr → 1/2

Answer:
- Genotypic ratio: 1 Rr : 1 rr
- Phenotypic ratio: 1 round : 1 wrinkled
- Number of offspring with round seeds: 2 out of 4
- Number with wrinkled seeds: 2 out of 4

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Problem 5: Cross between Homozygous Recessive and Homozygous Dominant

#### Cross: gg x GG

| | G | G |
|-------|-------|-------|
| g | Gg | Gg |
| g | Gg | Gg |

All offspring: Gg

Phenotype: All green (since G is dominant)

Answer:
- Genotypic ratio: All Gg
- Phenotypic ratio: All green
- Number of green offspring: 4 out of 4
- Number of yellow: 0

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Problem 6: Cross between Homozygous Dominant and Homozygous Recessive

This is the same as Problem 5 but reversed.

#### Cross: GG x gg

| | g | g |
|-------|-------|-------|
| G | Gg | Gg |
| G | Gg | Gg |

All offspring: Gg

Phenotype: All green

Answer:
- Genotypic ratio: All Gg
- Phenotypic ratio: All green
- Number of green offspring: 4 out of 4
- Number of yellow: 0

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Problem 7: Cross between Two Heterozygous Parents

This is similar to Problem 1 and 2, but now both parents are heterozygous for both traits (color and shape). This is a dihybrid cross.

#### Cross: GgRr x GgRr

We need to make a 4x4 Punnett square or use the rule of multiplication.

Gametes from each parent: GR, Gr, gR, gr

Let’s do the cross:

| | GR | Gr | gR | gr |
|-------|--------|--------|--------|--------|
| GR| GGRR | GGRr | GgRR | GgRr |
| Gr| GGRr | GGrr | GgRr | Ggrr |
| gR| GgRR | GgRr | ggRR | ggRr |
| gr| GgRr | Ggrr | ggRr | ggrr |

Now let’s count phenotypes:

- Green & Round: G_ R_ → 9/16
(GGRR, GGRr, GgRR, GgRr)
- Green & Wrinkled: G_ rr → 3/16
(GGrr, Ggrr)
- Yellow & Round: gg R_ → 3/16
(ggRR, ggRr)
- Yellow & Wrinkled: gg rr → 1/16
(ggrr)

Answer:
- Phenotypic ratio: 9:3:3:1
- Number of green-round: 9
- Green-wrinkled: 3
- Yellow-round: 3
- Yellow-wrinkled: 1

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Summary of Answers:

| Problem | Cross Type | Phenotypic Ratio | Key Results |
|--------|-------------------------------|------------------------------|-------------|
| 1 | Gg x Gg | 3 green : 1 yellow | 3 green, 1 yellow |
| 2 | Rr x Rr | 3 round : 1 wrinkled | 3 round, 1 wrinkled |
| 3 | GG x Gg | All green | 4 green, 0 yellow |
| 4 | rr x Rr | 1 round : 1 wrinkled | 2 round, 2 wrinkled |
| 5 | gg x GG | All green | 4 green, 0 yellow |
| 6 | GG x gg | All green | 4 green, 0 yellow |
| 7 | GgRr x GgRr (dihybrid) | 9:3:3:1 (green-round, etc.) | 9 green-round, 3 green-wrinkled, 3 yellow-round, 1 yellow-wrinkled |

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If you have specific questions about any of these problems or need help filling out the Punnett squares visually, feel free to ask!