Inherited Disorders

• Some disorders can be inherited from your parents. Many of these can be screened for in embryos
• Cystic fibrosis is caused by a recessive allele
• Cystic fibrosis is a genetic disorder of the cell membranes. It results in the body producing a lot of thick mucus in the air passages and in the pancreas
• The allele which causes cystic fibrosis is a recessive allele, 'f' carried by about 1 person in 25. Because it's recessive, people with only one copy of the allele won't have the disorder - they're known as carriers

  
• For a child to have the disorder, both parents must be either carriers or have the disorder themselves. As the diagram shows, there is a 1 in 4 chance of a child having the disorder if both parents are carriers

  
• Polydactyly is caused by a dominant allele
• Polydactyly is a genetic disorder where a baby's born with extra fingers or toes. It doesn't usually cause any other problems so isn't life-threatening

  
• The disorder polydactyly is caused by a dominant allele, 'D', and so can be inherited if just one parent carries the defective allele. The parent that has the defective allele will have the condition too since the allele is dominant

  
• As the genetic diagram shows, there's a 50% chance of a child having the disorder if one parent has one D allele

  
• Embryos can be screened for genetic disorders
• 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 disorder 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
• There are lots of ethical, social and economic concerns surrounding embryo screening
• 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 against embryonic screening

  • It implies that people with genetic problems are 'undesirable' - this 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
• 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)