Punnett Squares and Eye Color by Simply Science | TPT - Free Printable

The image you've uploaded shows a Punnett square used in genetics to predict the genotypes and phenotypes of offspring from a cross between two parents.

Let's analyze it step by step:

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🔬 Understanding the Punnett Square

The Punnett square is for a monohybrid cross involving eye color, where:
- B = dominant allele for brown eyes
- b = recessive allele for blue eyes

The parents are both heterozygous (Bb) — meaning each parent has one dominant (B) and one recessive (b) allele.

The square shows the possible combinations of alleles from the parents:

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

Wait — this appears to have an error. Let's correct it.

Actually, the correct setup should be:

```
B b
-----------
B | BB Bb
-----------
b | Bb bb
```

But in your image, the bottom-left box says BB, which is incorrect. It should be Bb.

So let's fix that.

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✔ Corrected Punnett Square

```
B b
-----------
B | BB Bb
-----------
b | Bb bb
```

Now, the four possible genotypes are:
- BB → 1 out of 4 → 25%
- Bb → 2 out of 4 → 50%
- bb → 1 out of 4 → 25%

---

🧬 Genotype and Phenotype Analysis

| Genotype | Probability | Phenotype |
|---------|-------------|------------------|
| BB | 1/4 | Brown eyes |
| Bb | 2/4 = 1/2 | Brown eyes |
| bb | 1/4 | Blue eyes |

So:
- Brown eyes: BB + Bb = 1/4 + 2/4 = 3/4 = 75%
- Blue eyes: bb = 1/4 = 25%

---

✘ Issue with Your Image

Your image says:
> "2/4 = 1/2 = 50% chance = genotype BB = phenotype brown eyes"

This is incorrect because:
- BB occurs only once, not twice.
- So BB = 1/4 = 25%, not 50%.

Then it says:
> "2/4 = 1/2 = 50% chance = genotype Bb = phenotype brown eyes"

This part is correct — Bb does appear twice (50%), and since B is dominant, Bb results in brown eyes.

But the first statement is wrong.

---

✔ Correct Interpretation

- Genotype BB: 1/4 → 25% → Brown eyes
- Genotype Bb: 2/4 → 50% → Brown eyes
- Genotype bb: 1/4 → 25% → Blue eyes

✔ Phenotype:
- Brown eyes: 75% (BB + Bb)
- Blue eyes: 25% (bb)

---

✔ Final Answer

There is a 75% chance that an offspring will have brown eyes and a 25% chance of having blue eyes.

Even though the image incorrectly states that BB occurs 50% of the time, the phenotypic conclusion about brown eyes being 50% is also incorrect — it should be 75%.

---

💡 Summary

- The Punnett square in the image is incorrect due to mislabeling.
- The correct probability of brown eyes is 75%, not 50%.
- The correct probabilities are:
- BB: 25% → brown eyes
- Bb: 50% → brown eyes
- bb: 25% → blue eyes

Let me know if you'd like a corrected version of the Punnett square!