Punnett Squares Practice Worksheets - Print & Digital

Let’s go step by step through each problem on the worksheet. I’ll solve them one at a time, clearly and simply.

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Problem 1: Pea plant with genotype Bb

We’re told to circle all words that describe “Bb”.

- A. Heterozygous → YES (two different alleles: B and b)
- B. Homozygous → NO (that would be BB or bb)
- C. True breeding → NO (true breeding means homozygous — always passes same allele)
- D. Purebred → NO (same as true breeding — homozygous)
- E. Hybrid → YES (hybrid = heterozygous in genetics)

✔ Answer: A and E

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Problem 2: Rabbit with genotype AA

Circle all words that describe “AA”.

- A. Heterozygous → NO (different alleles needed)
- B. Homozygous → YES (both alleles are A)
- C. True breeding → YES (will always pass A, so offspring will show same trait if crossed with similar)
- D. Purebred → YES (same as true breeding — homozygous)
- E. Hybrid → NO (hybrid = heterozygous)

✔ Answer: B, C, D

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Problem 3: Purple flowers dominant over white. List all possible genotypes for purple flower.

Purple is dominant → let’s say P = purple, p = white.

To have purple phenotype, you need at least one P.

So possible genotypes: PP or Pp

✔ Answer: PP, Pp

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Problem 4: Yellow peas dominant over green. List all possible genotypes for green pea.

Green is recessive → only shows up if no dominant allele.

So must be: yy (if Y = yellow, y = green)

✔ Answer: yy

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Problem 5: Tallness dominant to short. Tell phenotype for each genotype.

Assume T = tall, t = short.

- TT → two tall alleles → tall
- Tt → one tall, one short → still tall (dominant wins)
- tt → two short → short

✔ Answers:
- TT → tall
- Tt → tall
- tt → short

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Problem 6: Grey fur dog (Gg) x black fur dog (gg)

Grey is dominant? Wait — it says grey fur dog is Gg, black is gg → so grey must be dominant (since Gg shows grey).

Cross: Gg × gg

Punnett Square:

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

Genotypes:
→ 2 Gg, 2 gg → so 50% Gg, 50% gg

Phenotypes:
→ Gg = grey, gg = black → 50% grey, 50% black

✔ Genotypes: Gg, gg
✔ Phenotypes: grey fur, black fur

*(Note: The worksheet already lists these under GENOTYPES and PHENOTYPES — we just confirm they match our square.)*

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Problem 7: Two hybrid grey dogs crossed (Gg × Gg)

Hybrid = heterozygous → Gg × Gg

Punnett Square:

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

Genotypes:
→ 1 GG, 2 Gg, 1 gg → GG, Gg, gg

Phenotypes:
→ GG = grey, Gg = grey, gg = black → 3 grey : 1 black

✔ Genotypes: GG, Gg, gg
✔ Phenotypes: grey fur, black fur

*(Again, worksheet lists these — we verify they’re correct.)*

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Problem 8: Two heterozygous curly haired guinea pigs crossed. Straight hair is recessive.

Curly is dominant → let’s say C = curly, c = straight.

Parents: Cc × Cc

Punnett Square:

| | C | c |
|-----|-----|-----|
| C | CC | Cc |
| c | Cc | cc |

Genotypes: CC, Cc, cc

Phenotypes:
→ CC = curly, Cc = curly, cc = straight → 3 curly : 1 straight

✔ Genotypes: CC, Cc, cc
✔ Phenotypes: curly hair, straight hair

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Problem 9: Purebred red flower × purebred white flower. Red is dominant.

Purebred red = RR
Purebred white = rr (since white is recessive)

Cross: RR × rr

All offspring: Rr

Genotype: Rr (only one possibility)

Phenotype: red (since R is dominant)

✔ Genotypes: Rr
✔ Phenotypes: red

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Problem 10: Heterozygous tall pea plant × homozygous short pea plant

Tall dominant → T = tall, t = short

Heterozygous tall = Tt
Homozygous short = tt

Cross: Tt × tt

Punnett Square:

| | t | t |
|-----|-----|-----|
| T | Tt | Tt |
| t | tt | tt |

Genotypes: Tt, tt

Phenotypes: tall, short

✔ Genotypes: Tt, tt
✔ Phenotypes: tall, short

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Problem 11: Parents worried baby was switched. Baby has blonde hair. Mother is homozygous brown hair. Father is heterozygous brown hair. Some family members have blonde hair. Did hospital make mistake?

First, assign letters:

Let B = brown (dominant), b = blonde (recessive)

Mother: homozygous brown → BB

Father: heterozygous brown → Bb

Possible children from BB × Bb:

| | B | b |
|-----|-----|-----|
| B | BB | Bb |
| B | BB | Bb |

All offspring: BB or Bb → both have brown hair (since B is dominant)

Blonde hair = bb → but neither parent can give a ‘b’ except father gives b half the time, but mother gives ONLY B → so child MUST get B from mom → so child is either BB or Bb → ALWAYS brown hair.

But baby has blonde hair → which requires bb → impossible from these parents.

Also, note: “Some members of the family have blonde hair” — that’s fine, maybe grandparents or cousins, but not from THIS couple.

✔ So yes — hospital made a mistake, because this couple cannot have a blonde-haired child.

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Final Answer:

Here are the answers to each problem in order:

1. A, E
2. B, C, D
3. PP, Pp
4. yy
5. TT → tall; Tt → tall; tt → short
6. Genotypes: Gg, gg; Phenotypes: grey fur, black fur
7. Genotypes: GG, Gg, gg; Phenotypes: grey fur, black fur
8. Genotypes: CC, Cc, cc; Phenotypes: curly hair, straight hair
9. Genotypes: Rr; Phenotypes: red
10. Genotypes: Tt, tt; Phenotypes: tall, short
11. Yes, the hospital made a mistake — two brown-haired parents (one homozygous, one heterozygous) cannot have a blonde-haired child.