Answered

Unattached earlobes are dominant to attached earlobes. Cleft chin is dominant to no cleft. Parents that are heterozygous for both traits are crossed.

Determine the ratio of offspring with the described trait to the total number of offspring:

Unattached earlobes and cleft chin [tex]$\square$[/tex]

Unattached earlobes and no cleft [tex]$\square$[/tex]

Attached earlobes and cleft chin [tex]$\square$[/tex]

Attached earlobes and no cleft [tex]$\square$[/tex]



Answer :

GinnyAnswer
Let's solve the problem step-by-step:

### Problem Analysis

We are dealing with a dihybrid cross involving two traits:

1. Earlobe type:
- Unattached earlobes (dominant)
- Denoted by "E"
- Attached earlobes (recessive)
- Denoted by "e"

2. Chin type:
- Cleft chin (dominant)
- Denoted by "C"
- No cleft chin (recessive)
- Denoted by "c"

The parents are heterozygous for both traits, which means their genotype is "EeCc."

### Step-by-step Solution

#### 1. Possible Gametes Formation

Each parent can produce the following combinations of gametes:
- EC (E from earlobe gene, C from chin gene)
- Ec (E from earlobe gene, c from chin gene)
- eC (e from earlobe gene, C from chin gene)
- ec (e from earlobe gene, c from chin gene)

#### 2. Punnett Square Construction

Using these gametes, we construct a 4x4 Punnett square to determine the genotypes of the offspring. The punnett square looks like this:

| | EC | Ec | eC | ec |
|-----------|------------|------------|------------|------------|
| EC | EECc | EECc | EeCc | Eecc |
| Ec | EeCc | EeCc | Eecc | Eecc |
| eC | EeCc | Eecc | eeCc | eec |
| ec | Eecc | Eecc | eeCc | eec |

#### 3. Phenotypes Determination

Next, we translate these genotypes into phenotypes:

1. Unattached earlobes and cleft chin (E_, C_):
- Corresponding genotypes: EECc, EeCc

2. Unattached earlobes and no cleft (E_, cc):
- Corresponding genotypes: Eecc

3. Attached earlobes and cleft chin (ee, C_):
- Corresponding genotypes: eeCc

4. Attached earlobes and no cleft (ee, cc):
- Corresponding genotypes: eec

#### 4. Counting Occurrences

Now, we tally the occurrences of each phenotype from the punnett square:

1. Unattached earlobes and cleft chin: 8 offspring
2. Unattached earlobes and no cleft: 4 offspring
3. Attached earlobes and cleft chin: 3 offspring
4. Attached earlobes and no cleft: 1 offspring

#### 5. Total Offspring

The total number of offspring is the sum of all the phenotype counts:
[tex]\[ 8 + 4 + 3 + 1 = 16 \][/tex]

#### 6. Ratio Calculation

Finally, calculate the ratio of each phenotype to the total number of offspring:

1. Unattached earlobes and cleft chin:
[tex]\[ \frac{8}{16} = 0.5 \][/tex]

2. Unattached earlobes and no cleft:
[tex]\[ \frac{4}{16} = 0.25 \][/tex]

3. Attached earlobes and cleft chin:
[tex]\[ \frac{3}{16} = 0.1875 \][/tex]

4. Attached earlobes and no cleft:
[tex]\[ \frac{1}{16} = 0.0625 \][/tex]

### Summary

The ratio of offspring with the described traits to the total number of offspring is:

- Unattached earlobes and cleft chin: [tex]\(0.5\)[/tex]
- Unattached earlobes and no cleft: [tex]\(0.25\)[/tex]
- Attached earlobes and cleft chin: [tex]\(0.1875\)[/tex]
- Attached earlobes and no cleft: [tex]\(0.0625\)[/tex]

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