Final answer:
A pedigree chart for Tony and Tina would depict the autosomal recessive inheritance pattern of cystic fibrosis, with both sets of parents being carriers (Aa) and Tony and Tina having potential genotypes of either AA or Aa. Their child's risk of having CF depends on if both Tony and Tina are carriers.
Step-by-step explanation:
The pedigree chart to represent the scenario where Tony has a sister with cystic fibrosis (CF), neither of his parents have CF, and Tony is expecting a child with Tina who also has a brother with CF, would illustrate the genetic risk of their child having CF. In autosomal recessive disorders like cystic fibrosis, two copies of the defective gene (aa) are necessary for the offspring to express the disease, while carriers have one copy of the normal gene and one copy of the mutant gene (Aa).
Tony, without the disease, might either be a carrier (Aa) or not (AA), since having a sister with CF indicates at least one mutant allele is in his family. His parents must both be carriers (Aa) since they do not have the disease but have a daughter with CF. Tina's brother's presence with CF implies that her parents are also carriers (Aa), making Tina either a carrier (Aa) or not (AA).
Their child has a chance of inheriting CF if both Tony and Tina are carriers. The Punnett square for two carriers (Aa x Aa) shows a 25% chance of a child having CF (aa), a 50% chance of being a carrier without symptoms (Aa), and a 25% chance of being unaffected and not a carrier (AA).
Possible Pedigree Genotypes
- Tony's sister (with CF): aa
- Tony's parents: Aa
- Tina's brother (with CF): aa
- Tina's parents: Aa
- Tony: AA or Aa
- Tina: AA or Aa
- Their child: AA, Aa, or aa
This scenario shows how autosomal recessive disorders can affect families and how the genotypes of individuals can be inferred from their familial relationships and phenotypes.