Inherited disorders

• What are inherited disorders?

  Conditions passed on through certain alleles
• What is polydactyly?

  • Condition with extra fingers or toes
  • Usually does not cause other problems
  • Caused by a dominant allele
• What happens if one allele is for polydactyly?

  You will have the disorder
• What is the genetic diagram outcome when crossing a heterozygous individual with a homozygous normal individual for polydactyly?

  • Gametes: 1 dominant polydactyly, 3 normal
  • Offspring: 2 heterozygous (polydactyly), 2 homozygous normal
  • Phenotype ratio: 1:1 (50% chance for polydactyly)
• How is cystic fibrosis inherited?

  • Caused by a recessive allele
  • Requires two copies of the allele to have the condition
  • Most people are homozygous dominant
  • 1 in 25 are heterozygous carriers
• What does the lowercase f represent in cystic fibrosis?

  The recessive allele causing cystic fibrosis
• What is the outcome of crossing two carriers for cystic fibrosis?

  • Parent phenotypes: both normal
  • Genotypes: both heterozygous
  • Offspring: 1 homozygous dominant, 2 heterozygous, 1 homozygous recessive
  • Phenotype ratio: 3 normal, 1 cystic fibrosis
• What is embryo screening?

  Checking embryo genes for genetic disorders
• What might happen if a genetic disorder is found during embryo screening?

  Parents may discard that embryo
• What are the advantages of embryonic screening?

  • Reduces overall suffering from health problems
  • Saves money on treating genetic disorders
• What are the concerns regarding embryonic screening?

  • Implies genetic problems are less desirable
  • Could increase prejudice against affected individuals
  • Potential future screening for non-health traits
• What laws exist in the UK regarding genetic screening?

  Many laws prevent screening for non-health traits
• What is the main ethical debate surrounding embryo screening?

  Whether it is right to discard embryos