Family Trees

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

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

  You might need to watch the video a couple of 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 does it mean if a person has one copy of the faulty allele for cystic fibrosis?

  They are a carrier
• How is polydactyly inherited?

  It is 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
• What does a family tree show?

  Phenotypes
• What is the genotype of person 2 who has cystic fibrosis?

  Lowercase e lowercase e
• What evidence supports that cystic fibrosis is caused by a recessive allele?

  Person 11 has cystic fibrosis, but neither parent does
• If persons 7 and 8 had another child, what is the chance that child would have 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?

  Because person 1 does not have polydactyly
• If person 6 and 7 have another child, what is the probability that the child will have polydactyly?

  50% or one in two
• What are the key differences between cystic fibrosis and polydactyly in terms of inheritance?

  • Cystic fibrosis is caused by a recessive allele.
  • Polydactyly is caused by a dominant allele.
  • Cystic fibrosis requires two copies of the faulty allele to express the disorder.
  • Polydactyly requires only one copy of the faulty allele to express the trait.
• What is the significance of carriers in genetic disorders?

  • Carriers have one copy of the faulty allele but do not express the disorder.
  • They can pass the faulty allele to their offspring.
  • Understanding carriers is crucial for predicting inheritance patterns in family trees.
• How do you use a Punnett square to determine probabilities of genetic traits?

  1. Identify the genotypes of the parents.
  2. Set up the Punnett square with the alleles.
  3. Calculate the probabilities of offspring genotypes.
  4. Interpret the results to find the likelihood of traits.
• What is the role of family trees in genetics?

  • Family trees visually represent inheritance patterns.
  • They show phenotypes of family members.
  • They help identify carriers and predict the likelihood of genetic disorders.