Polydactyly

• What is the inherited disorder discussed in this video?

  Polydactyly II
• What is a characteristic of polydactyly II?

  Extra fingers or toes
• What type of allele causes polydactyly II?

  Dominant allele
• Can a person be a carrier of the polydactyly allele?

  No, you cannot be a carrier
• What are the genotypes of a man who is heterozygous for the polydactyly allele?

  One polydactyly allele, one normal allele
• What are the genotypes of a woman who is homozygous for the normal allele?

  Two normal alleles
• What is the expected ratio of offspring in the cross between a heterozygous man and a homozygous normal woman?

  1 to 1 ratio
• What percentage of the offspring will have polydactyly from the described cross?

  50%
• What percentage of the offspring will be unaffected by polydactyly?

  50%
• What is the nature of the probabilities in genetic crosses?

  They are just probabilities
• What is one solution to inherited disorders mentioned in the video?

  Embryo screening
• What happens during embryo screening?

  Embryos are tested for inherited disorders
• What happens to embryos that do not have defective alleles?

  They are implanted into the woman
• What is a major ethical concern regarding embryo screening?

  Destruction of healthy embryos
• What is a potential future use of embryo screening that raises ethical concerns?

  Producing offspring with desirable features
• What is gene therapy?

  Correcting faulty alleles to treat disorders
• Is gene therapy currently a standard treatment?

  No, it is still experimental
• What are the steps to complete a Punnett square for polydactyly II?

  1. Identify the alleles of the parents
  2. Set up the Punnett square
  3. Fill in the square with possible offspring genotypes
  4. Calculate the phenotypes and ratios
• What are the issues surrounding embryo screening?

  • High cost of screening
  • Ethical concerns about embryo destruction
  • Potential for selecting desirable traits
• What are the characteristics of dominant alleles?

  • Expressed in the phenotype if present
  • Cannot be a carrier
  • Only one copy needed for expression