Family Trees

• What causes some inherited disorders?

  A recessive allele
• Which inherited disorder is caused by a recessive allele?

  Cystic fibrosis
• What must a person with cystic fibrosis inherit?

  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, but don't have it
• What causes Polydactyly?

  A dominant allele
• How many faulty alleles must a person inherit to develop Polydactyly?

  One faulty allele
• Why does a person with only one copy of the Polydactyly allele still develop the condition?

  The Polydactyly allele is dominant
• What do family trees show?

  Phenotypes
• What genotype must person 2 have if they have cystic fibrosis and the cystic fibrosis allele is recessive?

  Lowercase e lowercase e
• If person 11 has cystic fibrosis but neither of their parents (persons 7 and 8) have cystic fibrosis, what does this suggest about the cystic fibrosis allele?

  It must be recessive
• If cystic fibrosis was caused by a dominant allele, what would have to be true of the parents of a child with cystic fibrosis?

  At least one parent would have it
• If persons seven and eight are both carriers for cystic fibrosis, what is the chance that their child will have cystic fibrosis?

  25%
• Why must person 3 have the genotype capital P lowercase P if they have polydactyly?

  Because they are heterozygous for the trait
• Why can't person 3 have inherited the poly dactyly allele from person 1?

  Person 1 does not have poly dactyly
• If person 6 and 7 have another child, what is the probability that the child will have polydactyly, given that person 6 has the genotype lowercase p lowercase p and person 7 has the genotype capital P lowercase p?

  50%
• Given the cross between a mother with genotype lowercase P lowercase P and a father with genotype capital P lowercase P, what is the probability of any offspring having poly dactyly?

  One and two (50%)