Edexcel A-Level Biology A 9BN0
Lifestyle, Health and Risk
Genes and Health
Voice of the Genome
Biodiversity and Natural Resources
On the Wild Side
Immunity, Infection and Forensics
Run for Your Life
Grey Matter
Genes and Health
Pedigree diagrams and the inheritance of cystic fibrosis
- 3 things to know
- Papers 1, 2 and 3
Overview
Recall questions on reading a pedigree, identifying carriers, and the inheritance pattern of cystic fibrosis.
What you need to know
Answer each one before you reveal it.
What is the inheritance pattern of cystic fibrosis?
In a genetic pedigree diagram, what do squares and circles represent?
Questions from this subtopic
Each one with the model answer underneath.
- 1
In a genetic pedigree diagram, what do squares and circles represent?
Model answer
Squares represent males and circles represent females.
- 2
How are affected individuals and mating pairs shown in a pedigree diagram?
Model answer
Shaded shapes indicate affected individuals, and horizontal lines connect mating pairs.
- 3
How can you identify a recessive condition from a pedigree diagram?
Model answer
A recessive condition can be identified when two unaffected parents produce an affected offspring.
- 4
What pattern in a pedigree indicates that a condition is inherited as dominant?
Model answer
Every affected individual has at least one affected parent.
- 5
What is a carrier in the context of genetic inheritance?
Model answer
A carrier is a heterozygous individual who possesses one recessive allele but does not express the recessive phenotype.
- 6
Which gene is mutated in cystic fibrosis, and what does it code for?
Model answer
The CFTR gene is mutated; it codes for a chloride ion channel protein.
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