Worksheet on Punnett squares for monohybrid, dihybrid, and sex-linked crosses in genetics.

Let’s solve each problem step by step.

---

Problem 1: Cystic Fibrosis

Ron is homozygous dominant → FF
Nancy is a carrier → Ff (heterozygous)

We need to find the probability their child has cystic fibrosis. Since it’s recessive, only ff genotype will have the disease.

Set up Punnett square:

Male alleles (Ron = FF) go on top → F and F
Female alleles (Nancy = Ff) go on left → F and f

Punnett Square:

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

Offspring genotypes:
- Top-left: F from mom + F from dad → FF
- Top-right: F from mom + F from dad → FF
- Bottom-left: f from mom + F from dad → Ff
- Bottom-right: f from mom + F from dad → Ff

So we get:
- 2 out of 4 = 50% FF
- 2 out of 4 = 50% Ff
- 0 out of 4 = 0% ff

Phenotypes:
- FF → no cystic fibrosis (dominant allele present)
- Ff → no cystic fibrosis (carrier, but not affected)
- ff → has cystic fibrosis → none in this cross

So probability child has cystic fibrosis = 0%

Genotypic Percents:
- 50% FF
- 50% Ff
- 0% ff

Phenotypic Percents:
- 100% no cystic fibrosis
- 0% has cystic fibrosis

Final answer for Problem 1: 0%

---

Problem 2: Freckles

Patty is homozygous dominant → SS
Charlie is homozygous recessive → ss

Freckles are dominant, so S = freckles, s = no freckles.

Punnett square:

Male alleles (Charlie = ss) → s and s (on top)
Female alleles (Patty = SS) → S and S (on left)

```
| s | s
---------------------
S | Ss | Ss
---------------------
S | Ss | Ss
```

All offspring: Ss

Genotypic Percents:
- 100% Ss

Phenotypic Percents:
- All have at least one dominant S → all have freckles → 100% with freckles

Probability children will have freckles = 100%

---

Final Answer:

Problem 1:
Genotypic Percents: 50% FF, 50% Ff, 0% ff
Phenotypic Percents: 100% no cystic fibrosis, 0% has cystic fibrosis
→ Probability child has cystic fibrosis: 0%

Problem 2:
Genotypic Percents: 100% Ss
Phenotypic Percents: 100% with freckles
→ Probability children will have freckles: 100%

Boxed final answers as requested:

For Problem 1: $\boxed{0\%}$
For Problem 2: $\boxed{100\%}$