Family trees

• What should you be able to do by the end of the video?

  Interpret information from family trees
• Why might interpreting family trees be tricky?

  You may need to watch the video multiple times
• 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 genotype does a carrier of cystic fibrosis have?

  One copy of the faulty allele
• How does a person with cystic fibrosis differ from a carrier?

  A person with cystic fibrosis has two faulty alleles
• What is the cause of polydactyly?

  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 regarding phenotypes and genotypes?

  A family tree shows phenotypes, not genotypes
• What is the genotype of person 2 who has cystic fibrosis?

  Lowercase e lowercase e
• Why is person 11's cystic fibrosis evidence of a recessive allele?

  Neither parent has cystic fibrosis
• What would happen if cystic fibrosis was a dominant trait?

  At least one parent would have cystic fibrosis
• What is the chance that persons 7 and 8 will have another child with cystic fibrosis?

  25% or one in four
• What is the genotype of person 3 who has polydactyly?

  Capital P lowercase p
• Why can't person 3 inherit the polydactyly allele from person 1?

  Person 1 does not have polydactyly
• What is the probability that persons 6 and 7 will have a child with polydactyly?

  50% or one in two
• What does the Punnett square show for cystic fibrosis carriers?

  Probability of offspring having cystic fibrosis
• What is the significance of the family tree in genetic studies?

  It helps track inheritance patterns