Practice Dihybrid Crosses With Guinea Pigs - Free Printable

Problem Description:

The image provided is a Punnett square for a dihybrid cross involving two traits: coat color and ear length. The parents are:

- Parent 1 (P1): BBLL (black coat, long ears)
- Parent 2 (P2): bbll (white coat, short ears)

The task is to fill in the Punnett square with the genotypes of the offspring and determine their phenotypes based on the given information.

Key Information:

1. Coat Color:
- BB: Black coat
- Bb: Black coat (dominant allele B is expressed)
- bb: White coat

2. Ear Length:
- LL: Long ears
- Ll: Long ears (dominant allele L is expressed)
- ll: Short ears

3. Gametes from Parents:
- Parent 1 (BBLL) produces gametes: BL
- Parent 2 (bbll) produces gametes: bl

4. Offspring Genotypes (F1):
- From the possible fertilizations shown, the F1 generation has the genotype BbLi (heterozygous for both traits).

5. Task:
- Fill in the Punnett square with the genotypes of the offspring.
- Determine the phenotypes of each offspring based on the genotypes.

---

Solution:

#### Step 1: Identify the Gametes
- Parent 1 (BBLL): Produces gametes BL.
- Parent 2 (bbll): Produces gametes bl.

#### Step 2: Set Up the Punnett Square
The Punnett square will have the gametes from Parent 1 along the top row and the gametes from Parent 2 along the left column.

| | BL | Bl | bL | bl |
|--------|--------|--------|--------|--------|
| BL | | | | |
| Bl | | | | |
| bL | | | | |
| bl | | | | |

#### Step 3: Fill in the Genotypes
Combine the alleles from the gametes to determine the genotypes of the offspring.

| | BL | Bl | bL | bl |
|--------|--------|--------|--------|--------|
| BL | BBLl | BBLl | BBLl | BBLl |
| Bl | BbLL | BbLl | BbLL | BbLl |
| bL | BbLL | BbLl | bbLL | bbLl |
| bl | BbLl | Bbll | bbLl | bblL |

#### Step 4: Determine the Phenotypes
Using the key information about dominant and recessive alleles:

- Coat Color:
- B_ (B present): Black coat
- bb: White coat

- Ear Length:
- L_ (L present): Long ears
- ll: Short ears

Now, analyze each genotype:

1. BBLl: Black coat, Long ears
2. BBLl: Black coat, Long ears
3. BBLl: Black coat, Long ears
4. BBLl: Black coat, Long ears
5. BbLL: Black coat, Long ears
6. BbLl: Black coat, Long ears
7. BbLL: Black coat, Long ears
8. BbLl: Black coat, Long ears
9. BbLL: Black coat, Long ears
10. BbLl: Black coat, Long ears
11. bbLL: White coat, Long ears
12. bbLl: White coat, Long ears
13. BbLl: Black coat, Long ears
14. Bbll: Black coat, Short ears
15. bbLl: White coat, Long ears
16. bblL: White coat, Long ears

#### Step 5: Fill in the Punnett Square with Phenotypes
Using the phenotypes determined above, fill in the Punnett square:

| | BL | Bl | bL | bl |
|--------|--------|--------|--------|--------|
| BL | Black, Long | Black, Long | Black, Long | Black, Long |
| Bl | Black, Long | Black, Long | Black, Long | Black, Long |
| bL | Black, Long | Black, Long | White, Long | White, Long |
| bl | Black, Long | Black, Short | White, Long | White, Long |

---

Final Answer:

The completed Punnett square with genotypes and phenotypes is as follows:

| | BL | Bl | bL | bl |
|--------|--------|--------|--------|--------|
| BL | BBLl (Black, Long) | BBLl (Black, Long) | BBLl (Black, Long) | BBLl (Black, Long) |
| Bl | BbLL (Black, Long) | BbLl (Black, Long) | BbLL (Black, Long) | BbLl (Black, Long) |
| bL | BbLL (Black, Long) | BbLl (Black, Long) | bbLL (White, Long) | bbLl (White, Long) |
| bl | BbLl (Black, Long) | Bbll (Black, Short) | bbLl (White, Long) | bblL (White, Long) |

$$
\boxed{
\text{See the filled Punnett square above.}
}
$$