Genetics Lecture Flashcards
4 reasons for referral to genetics
- FHx of genetic conditions
- Diagnosis of genetic conditions
- Managements of genetic conditions
- Genetic counselling (aid decision making, increase understanding)
2 broad categories of pregnancy testing/screening
- Targeted
- Whole population
6 types of genetic screening
- Antenatal
- Neonatal
- Child
- Adult
- Pre-pregnancy
- In maturity
4 pregnancy related genetics screening
- Chorionic villus sampling
- Amniocentesis
- Pre-implantation genetic diagnosis
- Non-invasive prenatal testing
Describe amniocentesis
-Amniotic fluid is withdrawn
-Undergoes centrifugation
-Separates into supernatant fluid (top) and foetal cells (bottom)
-Foetal cells undergo biochemical tests and cell culture
-Gives a karyotype several weeks later
(14-16 weeks)
Describe chorionic villus sampling
Biopsy of chorionic villus gives next day karyotype (8-10 weeks)
Risk of miscarriage associated with amniocentesis + chorionic villus sampling
0.5-1%
Chorionic villus sampling has > risk than amniocentesis
Main difference between chorionic villus sampling and amniocentesis
- Amniocentesis done at 14-16 weeks vs chorionic villus sampling 8-10 weeks
- Amniocentesis gives karyotype in several weeks vs chorionic villus sampling next day
Describe duchenne muscular dystrophy
- X-linked
- Fatal early in adult life
- Carrier testing (prenatal and pre-implantation diagnosis)
Describe the screening for down syndrome
- Maternal age
- Triple screening
- CUBS screening
- Selection for amniocentesis
- Free natal DNA (private £500, coming to NHS, risk of error but high negative predictive value)
4 common recessive disorder that raise concern
- Cystic fibrosis (n. Europe)
- Sickle cell disease (Africa)
- Thalassaemia (Mediterranean, Asia)
- Breast/ovarian cancer BRCA1
3 carrier testings available by targeted testing in the UK
- CF mutation analysis (80-90% sensitive)
- Haemoglobinopathy
- Tay-sachs enzyme activity (disease that progressively destroys neurons)
Describe Tay-Sachs disease
- Progressive lysosomal storage disease
- Hex-A deficiency results in build up of lipid GM ganglioside (esp. in nerve cells of brain)
- Baby usually develops normally till ~6months
- Progressive neurological deterioration, usually fatal by 3-5 years
3 newborn screenings
- Clinical exam
- Hearing
- Blood spot
3 reasons to screen babies
- To enable early detection of pre-symptomatic babies
- To enable early treatment to improve health
- To reduce anxiety cause by uncertainty over symptoms before a diagnosis is made