Family trees

• What are family trees sometimes called?

  Family pedigrees
• What type of disorder is cystic fibrosis?

  Recessive inherited disorder
• What does it mean for cystic fibrosis to be recessive?

  You need two cystic fibrosis alleles to have it
• How are cystic fibrosis alleles represented?

  Lowercase f
• How is the healthy version of the cystic fibrosis allele represented?

  Uppercase F
• What genotype indicates a person has cystic fibrosis?

  Homozygous recessive genotype
• What genotype indicates a carrier of cystic fibrosis?

  Heterozygous genotype
• What does a shaded shape in a family pedigree represent?

  Person has the condition
• What does an empty shape in a family pedigree represent?

  Person doesn't have the condition
• What do half-shaded shapes indicate in a family pedigree?

  Person is a carrier
• What should you be given alongside a family pedigree in an exam?

  A key explaining the symbols
• What does each new row in a family tree represent?

  A new generation
• How can you determine the genotype of each person in a pedigree?

  By using the diagram and key
• What does a horizontal line connecting two shapes in a pedigree indicate?

  They are a couple
• What is the genotype of Jenny in the family tree?

  Homozygous dominant (capital F capital F)
• What is the genotype of Paul in the family tree?

  Heterozygous (capital F lowercase f)
• What are the genotypes of Anna and Lucy?

  Both are heterozygous (capital F lowercase f)
• What are the genotypes of Ron and Harry?

  Both are homozygous dominant (capital F capital F)
• What is the genotype of Sam's wife?

  Homozygous recessive (lowercase f lowercase f)
• What is the chance of Lucy and Jack's baby having cystic fibrosis?

  1 in 4 or 25%
• What are the key components of a family pedigree?

  • Circles for females
  • Squares for males
  • Shaded shapes for affected individuals
  • Half-shaded shapes for carriers
  • Key explaining symbols
• What genotypes do Lucy and Jack have?

  Both are heterozygous (capital F lowercase f)
• What is the process to determine the chance of a baby having cystic fibrosis from a pedigree?

  1. Identify parents' genotypes
  2. Draw a Punnett square
  3. Fill out the Punnett square
  4. Calculate probabilities from the results
• How do you interpret a family pedigree for cystic fibrosis?

  • Identify genotypes based on shading
  • Determine carriers and affected individuals
  • Understand generational relationships
• What are the implications of being a carrier for cystic fibrosis?

  • No symptoms of the disease
  • Can pass the allele to offspring
  • Important for genetic counseling