Family trees

• What are family trees sometimes called?

  Family pedigrees
• What type of disorder is cystic fibrosis?

  Recessive inherited disorder
• How many cystic fibrosis alleles are needed to have the disease?

  Two cystic fibrosis alleles
• How are cystic fibrosis alleles represented?

  Lowercase f for recessive alleles
• What does a capital F represent in cystic fibrosis genetics?

  Healthy version of the allele
• What genotype indicates a person has cystic fibrosis?

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

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

  Carrier of the condition
• What do circles and squares represent in a family pedigree?

  Circles for females, squares for males
• How do you determine the genotype of individuals in a pedigree?

  By analyzing the symbols and shading
• What does each new row in a family tree represent?

  A new generation
• What does a horizontal line connecting two shapes indicate?

  They are a couple
• What genotype does an unaffected female have?

  Homozygous dominant genotype
• What genotype does a male carrier of cystic fibrosis have?

  Heterozygous genotype
• What is the genotype of a female with cystic fibrosis?

  Homozygous recessive genotype
• What is the chance of Lucy and Jack's baby having cystic fibrosis?

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

  Both are heterozygous carriers
• How do you set up a Punnett square for Lucy and Jack?

  Put Lucy's alleles on the left
• What does the Punnett square reveal about Lucy and Jack's baby?

  Probability of genotypes and phenotypes
• What does a shaded shape indicate in a family pedigree?

  Person has the condition
• What are the key components of a family pedigree?

  • Circles represent females
  • Squares represent males
  • Shaded shapes indicate affected individuals
  • Half-shaded shapes indicate carriers
  • Key explains symbols used
• What are the genotypes associated with cystic fibrosis?

  • Homozygous recessive: has cystic fibrosis
  • Heterozygous: carrier of cystic fibrosis
  • Homozygous dominant: unaffected
• How do you calculate the probability of a child having cystic fibrosis?

  1. Identify parents' genotypes
  2. Set up a Punnett square
  3. Analyze the results for probabilities