Unattached earlobes are dominant to attached earlobes. A 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]$\quad$[/tex]

Unattached earlobes and no cleft: [tex]$\quad$[/tex]

Attached earlobes and cleft chin: [tex]$\quad$[/tex]

Attached earlobes and no cleft: [tex]$\quad$[/tex]

Certainly! Let's break down the problem to understand the inheritance of the two traits: earlobe attachment and the presence of a cleft chin.

### Genetic Notation
- Unattached earlobes (U) are dominant over attached earlobes (u).
- Cleft chin (C) is dominant over no cleft chin (c).

### Parental Genotypes
Both parents are heterozygous for both traits, meaning their genotypes are:
- Parent 1: UuCc
- Parent 2: UuCc

### Punnett Square Analysis
To determine the offspring genotypes, we need to create a Punnett square, where we consider all possible combinations of the alleles from each parent.

Here are the combinations of alleles each parent can contribute:
- Parent 1 can produce four possible gametes: UC, Uc, uC, and uc.
- Parent 2 can also produce the same four possibilities: UC, Uc, uC, and uc.

By using a Punnett square, we calculate each possible combination of these alleles:

| | UC | Uc | uC | uc |
|-------|-------|-------|-------|-------|
| UC| UUCC | UUCc | UuCC | UuCc |
| Uc| UUCc | UUcc | UuCc | Uucc |
| uC| UuCC | UuCc | uuCC | uuCc |
| uc| UuCc | Uucc | uuCc | uucc |

### Phenotype Ratios
From the Punnett square, we can determine how frequently each phenotype appears:

1. Unattached earlobes and cleft chin (U-C-):
This phenotype has any combination of at least one dominant allele for both traits:
- UUCC, UUCc, UuCC, UuCc
Counting these:
- 9 combinations out of 16 result in unattached earlobes and a cleft chin.

2. Unattached earlobes and no cleft chin (U-cc):
This phenotype requires at least one dominant allele for unattached earlobes and two recessive alleles for no cleft chin:
- UUcc, Uucc
Counting these:
- 3 combinations out of 16 result in unattached earlobes and no cleft chin.

3. Attached earlobes and cleft chin (uuC-):
This phenotype requires two recessive alleles for attached earlobes and at least one dominant allele for cleft chin:
- uuCC, uuCc
Counting these:
- 3 combinations out of 16 result in attached earlobes and a cleft chin.

4. Attached earlobes and no cleft chin (uucc):
This phenotype requires two recessive alleles for both traits:
- uucc
Counting these:
- 1 combination out of 16 results in attached earlobes and no cleft chin.

### Final Ratios
Summarizing the phenotype ratios:
- Unattached earlobes and cleft chin: 9 out of 16
- Unattached earlobes and no cleft chin: 3 out of 16
- Attached earlobes and cleft chin: 3 out of 16
- Attached earlobes and no cleft chin: 1 out of 16

So the final phenotype ratio is:
[tex]\[ 9 : 3 : 3 : 1 \][/tex]