What is genetic testing?
The analysis of DNA, RNA, chromosomes, proteins etc. in order to dtect alterations related to a heritable disorder.
Direct testing
Looking for mutations
Cytogenetic testing
examines the number/structure of chromosomes
Biochemical testing
Assaying metabolites
Is genetic testing just like any other medical test?
No
- Very complex process
- It is performed only once and is your permanent health record
- Diagnostic testing:
- Pre-diagnostic testing
- Confirming to a patient with a condtion who already ahs symptoms
- Offered to asymptomatic individuals who has a family history of a geentic disorder
Pre-implantation genetic diagnosis:
Pre-natal diagnosis
Pre-symptomatic genetic testing
- Biopsy - removing a part of tissue/cell
- Genetic testing of the foetus
- After baby is born - undergo testing
Pre-natal diagnosis
Genetic testing of the foetus. It is very controversial due to abortion rates increasing
Prenatal diagnosis in Down-syndrome: Non-invasive testing
What is it?
What week can it be performed?
What happens to AFP, inhibin A and hCG and oestriol
Safe blood testing for pregnant women
AFP is low
Inhibin A and hCG is high
Oestriol is low
–> in down syndrome
Gives you a risk score on the diagonsis
2 Methods of prenatal diagnosis? Invasive testing:
Amniocentesis
Chorionic villus sampling (CVS)
–> both are associated with a small risk of fetal loss.
What is amniocentesis?
What week can it be performed?
- Detecting chromosome abnormalities in amniotic fluid via needle
- Enzyme measurements (AFP for neural tube defects), DNA studies, in combination with ultrasound.
14-16th week - even ealy as 10 weeks
Chorionic villus sampling (CVS) involves:
What week is it performed? (pregnancy)
is it invasive or non-invasive?
biopsy of tissue - removing a small piece from the placenta to detect chromosomal abnormalities.
~10-14 weeks
Invasive
Pre-implantation genetic diagnosis (PGD):
PGD is the use of in vitro fertilisation (IVF) and genetic testing to select embryos free of a specific genetic condition for transfer to the uterus (biopsy)
Pre-implantation genetic diagnosis molecular analysis can be undertaken by:
PCR and cytogenetic analysis by FISH, SNP arryas, array CGH
- Unaffected embryo is transferred to the uterus of the mother
- Affected embryos is discarded, raising ethical issues.
Treatment of mutation carriers
People at risk can be screened for symptoms of the disorder
May lead to:
Change in lifestyle
Drug treatment
Prophylactic surgery
