Polydactyly

• What allele is polydactyly caused by?

  dominant allele
• Polydactyly is a genetic disorder where a baby is born with 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
• Embryo screening involves testing embryos for inherited disorders and implanting only those without defective alleles
• Issues around embryo screening

  • Expensive
  • Large number of embryos created but only a small number implanted, meaning healthy embryos are destroyed
  • Potential to screen for desirable features like height or intelligence, which many find unethical
• Gene therapy is the use of genetic techniques to treat inherited disorders, but is still experimental