Polydactyly

• Polydactyly II


  Inherited disorder where people have extra fingers or toes
• Polydactyly II


  • Caused by a dominant allele
  • A person with one copy of the polydactyly allele and one copy of the normal allele will have polydactyly
  • You cannot be a carrier of the polydactyly allele
• Cross between a man heterozygous for the polydactyly allele and a woman homozygous for the normal allele


  1. 50% of offspring are heterozygous for the polydactyly allele and have polydactyly

  2. 50% of offspring are unaffected by polydactyly
• The ratio of polydactyly to unaffected offspring is 1:1
• Embryo screening tests embryos for inherited disorders
• Embryos without defective alleles are implanted
• Issues with embryo screening

  • Expensive
  • Large number of embryos created but only a small number implanted, so some healthy embryos are destroyed
  • Potential to screen for desirable features like height or intelligence, which many find unethical
• Gene therapy can correct faulty alleles to treat inherited disorders, but is still experimental