Family Trees

• What is cystic fibrosis caused by?

  A recessive allele
• What must a person inherit to have cystic fibrosis?

  The faulty allele from both parents
• What does it mean if a person has one copy of the faulty allele?

  They are a carrier
• How many copies of the faulty allele does a person with cystic fibrosis have?

  Two copies
• What is polydactyly caused by?

  A dominant allele
• How many copies of the faulty allele must a person inherit to develop polydactyly?

  Only one copy
• What does a family tree show?

  Phenotypes, not genotypes
• What are the key characteristics of cystic fibrosis and polydactyly inheritance?

  • Cystic fibrosis: recessive allele, both parents must carry
  • Polydactyly: dominant allele, one parent can pass it
• What is the significance of family trees in genetics?

  • Show inheritance patterns
  • Indicate phenotypes of individuals
  • Help determine genotypes indirectly