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 is a carrier of cystic fibrosis?

  They have one copy of the faulty allele
• How is polydactyly caused?

  By a dominant allele
• How many copies of the faulty allele are needed for polydactyly to develop?

  One copy from one parent
• What does a family tree show?

  Phenotypes only
• What would happen if cystic fibrosis was a dominant trait?

  At least one parent would have cystic fibrosis
• What are the key characteristics of cystic fibrosis and polydactyly inheritance?

  • Cystic fibrosis: recessive allele, both parents must carry faulty allele
  • Polydactyly: dominant allele, only one parent needs to carry faulty allele
• What is the significance of family trees in genetics?

  • Show phenotypes of individuals
  • Help determine inheritance patterns
  • Useful for predicting probabilities of traits
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