Genetics Flashcards
Why are people referred to genetics?
- Family history genetic condition in relatives
- Diagnosis of genetic conditions (known / unknown)
- Management of genetic conditions
- Genetic counselling
What do people need to know before undergoing a genetic test?
- What test is for / what’s the point in having it done?
- How likely is it to be positive
- What happens if its positive
- What if its negative
- What if false positive / false negative
- Implications for other family members of positive results
- DNA stored
What types of pregnancy testing/screening are there?
- Targetted
- Whole population
When may someone undergo genetic screening?
- Antenatal
- Neonatal
- Child
- Adult
- Pre-pregnancy
- In maturity
What types of genetic testing is available in relation to reproducing?
- Test at birth
- Chorionic villus sampling
- Amniocentesis
- Pre-implantation genetic diagnosis
- Adoption
- Gamete donation
- Non invasive prenatal testing
When can non invasive prenatal testing be performed?
Around week 10
What is the inheritance of Duchenne muscular dystrophy?
X-linked
What types of genetic testing are associated with Ducehnne muscular dystrophy?
- Carrier testing
- Prenatal diagnosis
- Pre-implantation diagnosis
What are the features of autosomal dominant inheritance?
- Each child has 50% chance of inheriting mutation
- No skipped generations
- Equally trasmitted
How is Down syndrome screened for?
- Maternal age
- Triple screening
- CUBS screening
- Selection for amniocentesis
- Free fetal DNA
Give examples of common recessive disorders that raise screening issues.
- N. Europe Cystic Fibrosis
- Africans Sickle Cell DiseaseS
- Mediterranean, Asia Thalassaemias
- Ashkenazi Jews Tay-Sachs disease
- CF W1282X
- Breast / ovarian cancer BRCA1
What targeted carrier testing is available in the UK?
- CF mutation analysis 80-90% sensitive
- Haemoglobinopathy MCV, Hb electrophoresis , sickledex
- Tay Sachs enzyme activity
What is CF caused by?
Defect of cellular chloride transport
How is CF diagnosed?
- Immunoreactive trypsin (first 6 weeks)
- Sweat test
- Genotyping
How can CF present?
- Lung infections
- Meconium ileus
- Pancreatic insufficiency
What is the prevalence of CF?
1 in 2,500
What is sickle cell disorder caused by?
Abnormal Hb gene
What does sickling cause?
- Pain+++
- Cold, dehydration, infections
- Jaundice, stroke, leg ulcers, eyes, kidneys
- Anaesthetic issues
What is Tay Sachs disease
Progressive, genetic, lysosomal storage disease.
What is the cause of Tay Sachs disease?
Hexosaminidase A (hex-A) deficiency results in the build up of lipid GM(2) ganglioside, esp. in nerve cells in the brain.
How does Tay Sachs disease present?
- Baby usually develops normally until about 6 months of age.
- Progressive neurological deterioration.
- Usually fatal by 3-5 years.
What is the epidemiology of Tay Sachs disease?
- 1in 25 Ashkenazi Jews are carriers
- 1 in 250 of the general population are carriers.
What is involved in new-born screening?
- Clinical examination
- hearing
- Blood spot
Why do we screen babies?
- To enable early detection of pre-symptomatic babies
- To enable early treatment to improve health
- To reduce anxiety caused by uncertainty over symptoms before clinical diagnosis is made
