Genetic Screening... But Why?

15.3.06

Many questions, information needed
• What happened, why, what caused it?
• Whose fault was it? What can I/we do?
• Will it get better, is there a treatment?
• Will it happen again? Worse next time?
• What are our options? Are there any tests?
• Who else it at risk? Can they be tested?
• What can I do? Who can help us?

Clinical genetics package
• Genetic nurses/counsellors, MDT, medics.
• Home visits, pre-clinic contact, family history.
• Information gathering and consent; set them at ease.
• Genetics clinic - investigation, assessment.

Autosomal recessive
• Affected siblings [males] = [females].
• Parents usually unaffected carriers.
• 25% recurrence risk.
• Syndromes tend to breed true.
• Consanguinity, isolated populations.
• Founder effect versus selective advantage.
• Very, very low mutation rate.
• Non-paternity more likely.

Autosomal recessive conditions
• Cystic fibrosis.
• Sickle cell, thalassaemia - contiguous.
• Albinism.
• Hunter syndrome.

CF and carriers
• Everyone carries ≈5 recessive genes.
• Eg. sickle cell, thalassaemia, CF, Tay-Sachs.
• Consanguinity, making people aware.
• Population screening? When? How?

Genetic screening programmes
• During antenatal care, Down's screening.
• Haemoglobinpathies.

What are we going to do?
• Do nothing.
• Denial, hope for best.
• Public Health agenda, ££ costs.
• Eugenics.
• Give people choices and chances.

Population screening programmes
• Guidelines for new programmes. Who decides?
• Impact of genetic screening on extending family.
• Public Health agenda? Eugenics, ethical issues.

Types of genetic disease
• Chromosome disorders.
• Structural re-arrangements, translocations.

How important are genetic diseases?
• Individually rare, collectively common.

Influence of nature and nuture
• Multi-factorial.

Objectives of medical genetics
• 1X, specialist opinion, syndrome diagnosis.

Variation in human genome
• Single nucleotide polymorphism (SNP).
• Highly polymorphic markers.
• Anonymous sequences.
• Not causing disease, simply genetic flags.
• Frequent SNPs every 500-1,000 base pairs.
• Makes us varied and interesting.

Human Genome Project - deliverables
• Pharmacogenetics.
• Decreased toxicity/tailor therapy.

Applying new technologies
• Diagnostic testing.