Genetic screening is testing a person's DNA for particular alleles, using labelled DNA probes and DNA hybridisation. Screening can identify:
• heritable conditions: alleles that cause genetic disorders, such as cystic fibrosis, sickle cell anaemia or Huntington's disease
• drug responses: alleles that affect how a person responds to a drug, so the most effective drug and dose can be chosen
• health risks: alleles that increase the risk of a disease, such as the BRCA1 and BRCA2 alleles linked to breast and ovarian cancer.Screening can be carried out on:
• adults, for example to find out whether someone is a carrier of a recessive allele before having children
• embryos produced by IVF (pre-implantation genetic diagnosis), so only embryos without a disease allele are implanted
• fetuses during pregnancy, using cells from the amniotic fluid or placenta
• newborn babies, from a small blood sample.Benefits: early diagnosis allows early treatment or preventive measures, such as more frequent check-ups, lifestyle changes or preventive surgery for people with a high-risk BRCA1 allele. People can also make informed decisions about having children.Issues: a positive result for a risk allele does not mean the person will definitely develop the disease, and the result may cause anxiety. For some conditions, such as Huntington's disease, there is no cure. There are also concerns about privacy, and about whether employers or insurers could use the results. Screening embryos raises ethical questions about which embryos are discarded.The results of screening are usually explained through genetic counselling.
• heritable conditions: alleles that cause genetic disorders, such as cystic fibrosis, sickle cell anaemia or Huntington's disease
• drug responses: alleles that affect how a person responds to a drug, so the most effective drug and dose can be chosen
• health risks: alleles that increase the risk of a disease, such as the BRCA1 and BRCA2 alleles linked to breast and ovarian cancer.Screening can be carried out on:
• adults, for example to find out whether someone is a carrier of a recessive allele before having children
• embryos produced by IVF (pre-implantation genetic diagnosis), so only embryos without a disease allele are implanted
• fetuses during pregnancy, using cells from the amniotic fluid or placenta
• newborn babies, from a small blood sample.Benefits: early diagnosis allows early treatment or preventive measures, such as more frequent check-ups, lifestyle changes or preventive surgery for people with a high-risk BRCA1 allele. People can also make informed decisions about having children.Issues: a positive result for a risk allele does not mean the person will definitely develop the disease, and the result may cause anxiety. For some conditions, such as Huntington's disease, there is no cure. There are also concerns about privacy, and about whether employers or insurers could use the results. Screening embryos raises ethical questions about which embryos are discarded.The results of screening are usually explained through genetic counselling.