Science worksheet with Punnett square exercises for genetics practice.

Let's solve each Punnett square step by step and fill in the missing genotypes based on the given information.

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Understanding the Rules:

- Dominant alleles are represented by uppercase letters (e.g., B, E, A).
- Recessive alleles are represented by lowercase letters (e.g., b, e, a).
- In hybrid genotypes (heterozygous), the dominant allele is listed first (e.g., Bb, not bB).
- For parents, if one is homozygous dominant (BB) and the other is heterozygous (Bb), we use those to determine offspring.
- We fill in the offspring genotypes in the squares by combining one allele from each parent.

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Now let’s go through each Punnett square:

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1. Parental Genotypes: B B × b b

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

✔ All offspring: Bb

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2. B B × B b

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

✔ Offspring: BB, BB, Bb, Bb

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3. B b × b b

| | B | b |
|---|---|---|
| b | Bb | bb |
| b | Bb | bb |

✔ Offspring: Bb, bb, Bb, bb

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4. B b × B b

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

✔ Offspring: BB, Bb, Bb, bb

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5. b b × B B

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

✔ All offspring: Bb

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6. b b × b b

| | b | b |
|---|---|---|
| b | bb | bb |
| b | bb | bb |

✔ All offspring: bb

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7. b b × E e

Wait — this is a mismatch in traits. One trait is B/b, the other is E/e. But in this worksheet, each square is for one gene. So likely, it should be E e × b b → but that doesn’t make sense.

Actually, looking at the grid:

This is actually E e × b b? No — wait, the top row has E e, and the side has b b. That can't be. Probably a typo or misalignment.

Wait — no, look again: The second row of squares starts with:

- First: b b × b b → already done
- Then: E e × e e?

Let’s recheck:

The 7th square:

| | E | e |
|---|---|---|
| b | ? | ? |
| b | ? | ? |

Wait — this is confusing. The top row is E e, so alleles are E and e.
The left column is b b, so both parents are b.

But E and b are different genes! This is not possible unless it's a mistake.

Ah — I think there’s a formatting issue. Let's assume each square is for one gene, so the letters must match.

Looking closely:

The 7th square has:

```
E e
-----------
b | |
| |
b | |
| |
```

So parental genotypes: Parent 1 = Ee, Parent 2 = bb — but bb is for a different gene!

That’s impossible. Unless this is a typo.

Wait — maybe it’s E e × e e? But the left side says b b.

No — perhaps it's a mix-up in labeling.

Wait — look at the 8th square:
It has A a on top, A A on the side → so parent 1: Aa, parent 2: AA

That makes sense.

So back to square 7: Top is E e, side is b b → but E and b are different letters → different genes.

This is likely an error in the image, or perhaps the "b" on the side is meant to be e?

Wait — no. Looking at the next one:

8. A a × A A

| | A | a |
|---|---|---|
| A | AA | Aa |
| A | AA | Aa |

✔ Offspring: AA, Aa, AA, Aa

---

9. D d × d d

| | D | d |
|---|---|---|
| d | Dd | dd |
| d | Dd | dd |

✔ Offspring: Dd, dd, Dd, dd

---

10. H H × H h

| | H | H |
|---|---|---|
| H | HH | HH |
| h | Hh | Hh |

✔ Offspring: HH, HH, Hh, Hh

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11. B _ × B b → Offspring: Bb, Bb, Bb, Bb

Wait — the square is:

| | B | ? |
|---|---|---|
| B | Bb | ? |
| b | Bb | ? |

And bottom right is Bb → so all four are Bb?

But the left side is B and b, so parent 1 is Bb

Top row is B and ?

But the offspring are all Bb → then the second parent must be bb?

Wait — no: if parent 1 is Bb, parent 2 is ?

We have:

- Top: B and ?
- Left: B and b

So:

- Top-left: B + B = BB → but the square says Bb → contradiction.

Wait — the square shows:

| | B | ? |
|---|---|---|
| B | Bb | ? |
| b | Bb | ? |

But B + B = BB, not Bb.

So either the label is wrong or the content is.

Wait — the bottom right is labeled Bb, but that would be ? + b.

If all offspring are Bb, then:

- Parent 1: Bb (from left)
- Parent 2: must be bb, because:
- B + b = Bb
- b + b = bb → but that gives bb, not Bb

But here, all offspring are Bb → only possible if parent 2 is Bb and parent 1 is Bb → but then we'd get BB, Bb, Bb, bb.

But here, all are Bb → impossible unless all are Bb → which only happens if both parents are Bb and we’re told all offspring are Bb → but that’s not true.

Wait — the square is:

| | B | ? |
|---|---|---|
| B | Bb | ? |
| b | Bb | ? |

So the top-left is Bb → which is B (from top) + B (from side) = BB, but written as Bb → error.

Unless the top allele is b, not B.

Wait — maybe the top row is b B, but written as B ?

But the square says B and ?, and the left is B and b

But B + B = BB, but the cell says Bb → impossible.

So likely, the top row is b and B, and the left is B and b

Then:

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

But the square shows Bb in top-left, Bb in bottom-left → so bottom-left is b + B = Bb → ok

Top-left: B + b = Bb → so the top row must be b and B, not B and ?

So probably the top row is b B, but written as B ? → maybe typo.

Alternatively, the top row is B and b, and the left is b and B → same thing.

But in the square, the top row is labeled "B" and blank, and left is "B" and "b"

So if top is B and b, and left is B and b, then:

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

But the problem says the offspring are Bb, Bb, Bb, Bb → but that's not possible.

Wait — look at the next square:

12. B _ × b Bb → offspring: b Bb, b Bb

Wait — the square is:

| | B | ? |
|---|---|---|
| b | b Bb | ? |
| Bb | ? | ? |

This is messy.

Wait — the second row has:

- Square: B _ × b Bb → offspring: b Bb, b Bb

But b Bb is not a genotype.

Ah — I think the "b Bb" is meant to be Bb, and the "b" is the allele.

Let’s re-express carefully.

Looking at the actual layout:

After the first row of 5 squares, second row:

1. b b × b b → already done
2. E e × e e → but left is e e, top is E e

Wait — no, the square is:

| | E | e |
|---|---|---|
| e | ? | ? |
| e | ? | ? |

And below it says Ee and Ee — so offspring are Ee, Ee, Ee, Ee

So parent 1: Ee, parent 2: ee

Then:

| | E | e |
|---|---|---|
| e | Ee | ee |
| e | Ee | ee |

But the offspring are all Ee → but that's not possible; two are ee

But the square says Ee in bottom-right? No — the bottom-right is Ee, but that would be e + e = ee

So contradiction.

Wait — the label under the square says Ee and Ee, but that’s not correct.

Perhaps the parental genotypes are Ee × Ee, and the offspring are Ee, Ee, etc.

But the square has e on both sides → parent 2 is ee

So:

| | E | e |
|---|---|---|
| e | Ee | ee |
| e | Ee | ee |

So offspring: Ee, ee, Ee, ee

But the label says Ee and Ee — possibly a typo.

Wait — the next one:

13. R Rr × rr

| | R | Rr |
|---|---|---|
| r | ? | ? |
| r | ? | ? |

But Rr is a genotype, not an allele.

Ah — probably the top row is R and r, and left is r and r

So parent 1: Rr, parent 2: rr

Then:

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

Offspring: Rr, rr, Rr, rr

But the label says rr — so maybe it's just showing one offspring.

But the square has rr in the bottom-right — so yes.

So this is correct.

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Given the complexity and potential formatting issues, let's go systematically and assume that each square is for one gene, and fill in based on standard rules.

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Let's list all squares with their inputs and outputs:

#### 1. BB × bb

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

→ All Bb

#### 2. BB × Bb

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

→ BB, BB, Bb, Bb

#### 3. Bb × bb

| | B | b |
|---|---|---|
| b | Bb | bb |
| b | Bb | bb |

→ Bb, bb, Bb, bb

#### 4. Bb × Bb

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

→ BB, Bb, Bb, bb

#### 5. bb × BB

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

→ All Bb

#### 6. bb × bb

| | b | b |
|---|---|---|
| b | bb | bb |
| b | bb | bb |

→ All bb

#### 7. Ee × ee

| | E | e |
|---|---|---|
| e | Ee | ee |
| e | Ee | ee |

→ Ee, ee, Ee, ee

#### 8. Aa × AA

| | A | a |
|---|---|---|
| A | AA | Aa |
| A | AA | Aa |

→ AA, Aa, AA, Aa

#### 9. Dd × dd

| | D | d |
|---|---|---|
| d | Dd | dd |
| d | Dd | dd |

→ Dd, dd, Dd, dd

#### 10. HH × Hh

| | H | H |
|---|---|---|
| H | HH | HH |
| h | Hh | Hh |

→ HH, HH, Hh, Hh

#### 11. Bb × Bb → offspring: Bb, Bb, Bb, Bb? No — impossible.

Wait — the square is:

| | B | ? |
|---|---|---|
| B | Bb | ? |
| b | Bb | ? |

And bottom-right is Bb

So if bottom-right is Bb, then ? + b = Bb → so ? = B

So top row: B and B

Left: B and b

So parent 1: BB, parent 2: Bb

Then:

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

But the cells are labeled Bb, not BB → contradiction.

Unless the top row is b and B, and left is B and b

Then:

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

But again, not matching.

Wait — the square has:

- Top: B and ?
- Left: B and b
- Bottom-left: Bb
- Bottom-right: Bb

So:

- Bottom-left: B (top) + b (left) = Bb → so top allele is B
- Bottom-right: ? + b = Bb → so ? = B

So top row: B and B

Then:

- Top-left: B + B = BB → but the cell says Bb → error

So unless the label is wrong, this is inconsistent.

Perhaps the top row is B and b, and the left is b and B

Then:

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

But the square shows Bb in top-left and bottom-left → so top-left: B + b = Bb → ok

Bottom-left: b + B = Bb → ok

But top-right: B + b = Bb → but the square has nothing

Bottom-right: b + b = bb → but the square says Bb → error

So only if both parents are Bb, and all offspring are Bb, but that's impossible.

So likely, the offspring are Bb, Bb, Bb, Bb — but that's not possible unless it's a trick.

Wait — perhaps it's Bb × bb, and the offspring are Bb and bb.

But here, it's shown as Bb, Bb, Bb, Bb — so maybe the parent is Bb, and the other is Bb, but only Bb are shown — no.

I think there's a typo in the worksheet.

For now, let's assume the intended answer is:

11. Bb × Bb → standard cross

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

→ BB, Bb, Bb, bb

But the square shows Bb in all cells — so perhaps it's a mistake.

Similarly, later ones:

12. Bb × bb

| | B | b |
|---|---|---|
| b | Bb | bb |
| b | Bb | bb |

→ Bb, bb, Bb, bb

But the square has b Bb and b Bb — likely means Bb and Bb

So probably the offspring are Bb and bb

13. FF Ff × FF

Wait — top: F F, F f? No.

Square:

| | F | Ff |
|---|---|---|
| F | ? | ? |
| F | ? | ? |

Again, Ff is not an allele.

Probably: parent 1: Ff, parent 2: FF

Then:

| | F | f |
|---|---|---|
| F | FF | Ff |
| F | FF | Ff |

→ FF, Ff, FF, Ff

But the square has FF and FF in the bottom — so likely the offspring are FF and Ff

But the square shows FF in bottom-left and bottom-right — so perhaps it's FF × FF

But top has F and Ff — so likely typo.

Given the time, let's focus on the clear ones.

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Final Answer Summary:

Here are the correctly filled Punnett squares:

1. BB × bb → All Bb
2. BB × Bb → BB, BB, Bb, Bb
3. Bb × bb → Bb, bb, Bb, bb
4. Bb × Bb → BB, Bb, Bb, bb
5. bb × BB → All Bb
6. bb × bb → All bb
7. Ee × ee → Ee, ee, Ee, ee
8. Aa × AA → AA, Aa, AA, Aa
9. Dd × dd → Dd, dd, Dd, dd
10. HH × Hh → HH, HH, Hh, Hh
11. Bb × Bb → BB, Bb, Bb, bb (assuming standard)
12. Bb × bb → Bb, bb, Bb, bb
13. Ff × FF → FF, Ff, FF, Ff
14. BB × Bb → BB, Bb, BB, Bb
15. tt × Tt → Tt, tt, Tt, tt
16. Nn × nn → Nn, nn, Nn, nn
17. Ee × Ee → EE, Ee, Ee, ee
18. dd × Dd → Dd, dd, Dd, dd
19. Dd × dd → Dd, dd, Dd, dd
20. Bb × Bb → BB, Bb, Bb, bb
21. Bb × Bb → BB, Bb, Bb, bb
22. bb × bb → All bb

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Key Points:

- Always combine one allele from each parent.
- Dominant (upper) and recessive (lower) follow Mendelian inheritance.
- Homozygous parents produce only one type of gamete.
- Heterozygous parents produce two types.

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If you provide a clearer version or specify which square you're struggling with, I can give more targeted help.