Dihybrid cross worksheet - Free Printable

Problem Description:

We are tasked with completing a Punnett square for a dihybrid cross between two heterozygous parents (YyTt) for the traits of seed color (yellow vs. green) and plant height (tall vs. short). The goal is to determine the genotypes and phenotypes of the offspring.

Step-by-Step Solution:

#### 1. Identify the Genotypes of the Parents:
- Both parents are heterozygous for both traits: YyTt.
- Y = Yellow seeds (dominant)
- y = Green seeds (recessive)
- T = Tall plant (dominant)
- t = Short plant (recessive)

#### 2. Determine the Gametes Produced by Each Parent:
- Since each parent has the genotype YyTt, they will produce gametes through independent assortment.
- The possible gametes are:
- YT, Yt, yT, yt

#### 3. Set Up the Punnett Square:
- The Punnett square will have 4 rows and 4 columns, resulting in 16 boxes (since there are 4 gametes from each parent).
- Place the gametes of one parent along the top row and the other parent along the left column.

#### 4. Fill in the Punnett Square:
- Combine the alleles from the gametes to fill in each box of the Punnett square.

| | YT | Yt | yT | yt |
|-------|-------|-------|-------|-------|
| YT| YYTT | YYTt | YyTT | YyTt |
| Yt| YYTt | YYtt | YyTt | Yytt |
| yT| YyTT | YyTt | yyTT | yyTt |
| yt| YyTt | Yytt | yyTt | yytt |

#### 5. Determine the Phenotypes of the Offspring:
- Use the key provided:
- Y = Yellow seeds (dominant)
- y = Green seeds (recessive)
- T = Tall plant (dominant)
- t = Short plant (recessive)
- Analyze each genotype to determine the phenotype:
- Yellow seeds: Any genotype with at least one Y (e.g., YY, Yy)
- Green seeds: Genotype with yy
- Tall plant: Any genotype with at least one T (e.g., TT, Tt)
- Short plant: Genotype with tt

- Phenotypes for each box:
- YYTT, YYTt, YyTT, YyTt: Yellow seeds, Tall plant
- YYtt, Yytt: Yellow seeds, Short plant
- yyTT, yyTt: Green seeds, Tall plant
- yytt: Green seeds, Short plant

#### 6. Summarize the Phenotypes:
- From the Punnett square, we can see the distribution of phenotypes:
- Yellow seeds, Tall plant: 9/16
- Yellow seeds, Short plant: 3/16
- Green seeds, Tall plant: 3/16
- Green seeds, Short plant: 1/16

Final Answer:

The Punnett square is filled as follows:

| | YT | Yt | yT | yt |
|-------|-------|-------|-------|-------|
| YT| YYTT | YYTt | YyTT | YyTt |
| Yt| YYTt | YYtt | YyTt | Yytt |
| yT| YyTT | YyTt | yyTT | yyTt |
| yt| YyTt | Yytt | yyTt | yytt |

The phenotypes of the offspring are:
- Yellow seeds, Tall plant: 9/16
- Yellow seeds, Short plant: 3/16
- Green seeds, Tall plant: 3/16
- Green seeds, Short plant: 1/16

$$
\boxed{\text{Yellow seeds, Tall plant: 9/16; Yellow seeds, Short plant: 3/16; Green seeds, Tall plant: 3/16; Green seeds, Short plant: 1/16}}
$$