Family Trees

• What is the purpose of the video on family trees?

  To interpret information from family trees.
• What is a key fact about family trees in genetics?

  • Family trees show phenotypes
  • Family trees do not show genotypes
• What type of allele causes cystic fibrosis?

  Recessive allele.
• What must a person inherit to have cystic fibrosis?

  They must inherit the faulty allele from both parents.
• What is the genotype of a person with cystic fibrosis?

  Lowercase e lowercase e.
• Why is cystic fibrosis considered to be caused by a recessive allele?

  Because neither parent has cystic fibrosis, indicating they are carriers.
• What would happen if cystic fibrosis was a dominant disorder?

  At least one parent would have to have cystic fibrosis.
• What is the probability of two carriers having a child with cystic fibrosis?

  25% or one in four.
• What is the genotype of a person with polydactyly?

  • Capital P lowercase P (heterozygous)
• Why must person 3 inherit their polydactyly allele from person 2?

  Because person 1 does not have polydactyly and cannot pass on the allele.
• What is the probability of person 6 and 7 having a child with polydactyly?

  50% or one in two.
• What is the significance of the Punnett square in genetics?

  • It predicts the probability of offspring genotypes
  • It visualizes genetic crosses