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 many copies of the faulty allele does a person with cystic fibrosis have?

  Two copies of the faulty allele
• 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 from one parent
• Why do both individuals with polydactyly show the characteristic?

  Because the polydactyly allele is dominant
• What does a family tree show?

  Phenotypes, not genotypes
• What would happen if cystic fibrosis was a dominant trait?

  At least one parent would have cystic fibrosis