Inherited Disorders

• Inherited Disorders


  Disorders that can be inherited from parents
• Many inherited disorders can be screened for in embryos
• Cystic Fibrosis


  Genetic disorder of the cell membranes resulting in the body producing a lot of thick sticky mucus in the air passages and in the pancreas
• Cystic Fibrosis


  • Caused by a recessive allele 'P'
  • Carried by about 1 person in 25
  • People with only one copy of the allele are carriers and don't have the disorder
  • For a child to have the disorder, both parents must be either carriers or have the disorder themselves
• Inheritance of Cystic Fibrosis

  1. Unaffected, but carrier (Ff)

  2. Unaffected, but carrier (Ff)

  3. Unaffected carrier (Ff)

  4. Has cystic fibrosis (ff)
• Polydactyly


  Genetic disorder where a baby is born with extra fingers or toes, doesn't usually cause other problems
• Polydactyly


  • Caused by a dominant allele 'D'
  • If one parent has the defective allele, they will have the condition
  • There is a 50% chance of a child having the disorder if one parent has one D allele
• Inheritance of Polydactyly


  1. Has polydactyly (Dd)

  2. Unaffected (dd)

  3. Has polydactyly (Dd)

  4. Unaffected (dd)
• During in vitro fertilisation (IVF), embryos are fertilised in a laboratory, and then implanted into the mother's womb
• Before being implanted, it's possible to remove a cell from each embryo and analyse its genes
• Many genetic disorders can be detected in this way, such as cystic fibrosis
• It's also possible to get DNA from an embryo in the womb and test that for disorders
• Concerns surrounding embryo screening

  • Ethical
  • Social
  • Economic
• Embryonic screening is quite controversial because of the decisions it can lead to
• For embryos produced by IVF, after screening, embryos with 'bad' alleles would be destroyed
• For embryos in the womb, screening could lead to the decision to terminate the pregnancy
• Arguments for embryonic screening

  • It will help to stop people suffering
  • Treating disorders costs the Government (and the taxpayers) a lot of money
  • There are laws to stop it going too far. At the moment parents cannot even select the sex of their baby (unless it's for health reasons)
• Arguments against embryonic screening

  • It implies that people with genetic problems are 'undesirable' which could increase prejudice
  • There may come a point where everyone wants to screen their embryos so they can pick the most 'desirable' one, e.g. they want a blue-eyed, blond-haired, intelligent boy
  • Screening is expensive