family trees

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

  Interpret information from family trees
• Why can 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 many copies of the faulty allele must a person inherit to have cystic fibrosis?

  Two copies
• 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
• What is the key fact about family trees regarding phenotypes and genotypes?

  A family tree only shows phenotypes, not genotypes
• 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
• What would happen if cystic fibrosis was a dominant trait?

  At least one parent would have to have cystic fibrosis
• What is the probability that persons 7 and 8 would 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 are the key characteristics of cystic fibrosis and polydactyly inheritance?

  Cystic Fibrosis:

  • Caused by a recessive allele
  • Requires two copies of the faulty allele to express the disorder

  
  

  Polydactyly:

  • Caused by a dominant allele
  • Requires only one copy of the faulty allele to express the trait
• What is the significance of family trees in genetics?

  • Show phenotypes of individuals
  • Help determine inheritance patterns
  • Useful for predicting probabilities of traits in offspring
• How do you use a Punnett square for cystic fibrosis and polydactyly?

  Cystic Fibrosis:

  • Both parents are carriers: 25% chance of affected child

  
  

  Polydactyly:

  • One parent affected (heterozygous) and one unaffected: 50% chance of affected child