Family Trees / Family Pedigrees

• What are family trees sometimes called?

  Family pedigrees
• What type of disorder is cystic fibrosis?


  A recessive inherited disorder
• How are cystic fibrosis alleles represented?


  With a lowercase f
• What does it mean for cystic fibrosis to be a recessive disorder?


  You need two cystic fibrosis alleles to have the disease
• What genotype indicates a person has cystic fibrosis?


  Homozygous recessive genotype (two lowercase f's)
• What genotype indicates a person is a carrier of cystic fibrosis?


  Heterozygous genotype (capital F lowercase f)
• What do circles and squares represent in a family pedigree?


  Circles represent females and squares represent males
• What does a shaded shape indicate in a family pedigree?


  The person has the condition
• What do half-shaded shapes indicate in a family pedigree?


  Somebody who is a carrier
• What should you do when given a family pedigree in an exam?


  Understand how the key works and determine the genotypes
• How are generations represented in a family tree?


  Each new row represents a new generation
• What does a horizontal line connecting two shapes in a family tree indicate?


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


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


  Capital F lowercase f (heterozygous)
• What are the genotypes of Anna and Lucy in the family tree?


  Both have the heterozygous genotype (capital F lowercase f)
• What are the genotypes of Ron and Harry in the family tree?


  Both have the homozygous dominant genotype (capital F capital F)
• What is the genotype of Sam's wife in the family tree?


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


  1 in 4 or 25% chance
• What genotypes do Lucy and Jack have?


  Both have the heterozygous genotype (capital F lowercase f)
• What is the process to determine the chance of a baby having cystic fibrosis using a Punnett square?


  1. Identify the genotypes of the parents.
  2. Draw a Punnett square.
  3. Place one parent's alleles on the left and the other on the top.
  4. Fill out the Punnett square.
  5. Analyze the results for probabilities.
• What are the key components of a family pedigree for cystic fibrosis?


  • Circles represent females, squares represent males.
  • Shaded shapes indicate affected individuals.
  • Half-shaded shapes indicate carriers.
  • Each row represents a new generation.
• How do you interpret a family pedigree?


  • Use the key to understand symbols.
  • Determine genotypes based on shading.
  • Identify relationships and generations.