Genetics Lecture Flashcards
What are the main reasons for referral to genetics?
FH in relatives
Diagnosis of genetic conditions
Management of genetic conditions
Genetic counselling
What are the main forms of genetic screening?
Antenatal Neonatal Child Adult Pre-pregnancy In maturity
What are the reproductive choices in genetic conditions?
Nothing/test at birth CVS Amniocentesis Pre-implantation genetic diagnosis Adoption Gamete donation Non-invasive prenatal testing
What is the risk of miscarriage in CVS/amnio?
CVS > amnio
0.5 - 1%
When is Non-invasive prenatal testing used?
10th week of pregnancy
Fragments of cell-free DNA in maternal blood
What is Duchenne Muscular dystrophy?
X-linked
Fatal as early adult
How do autosomal dominant conditions present?
Each child 50% chance
No skipped generations
Equal for men and women
How is Down’s syndrome screened for?
Maternal age
Triple Screening
CUBS screening
Amniocentesis/fetal DNA
Which recessive disorders raise screening issues?
CF (N. europe) W1282X Sickle cell (African) Thalassaemia (Mediterranian, Asia) Tay-Sachs (Ashkenazi Jews) BRCA1
How is CF detected?
Mutation analysis
How sensitive is mutation analysis for CF?
80-90%
How is Sickle Cell detected?
Haemoglobinpathy MCV
Hb Electrophoresis
Sickledex
How is Tay-Sachs detected?
Enzyme activity
How common is CF?
1:2500
How does CF present in newborns?
Meconium ileus
Lung infections
Pancreatic insufficiency
How is CF diagnosed?
Immunoreactive trypsin
Sweat test
Genotyping
What is Sickle Cell disease?
Abnormal HB gene
How does Sickle Cell disease present?
Pain +++ Cold Dehydration INfections Jaundice Stroke, leg ulcers Eye problems Anaesthetic issues
What is Tay-Sachs disease?
Progessive genetic Lysosomal storage disease
Hexosaminidase deficiency results in build of of lipids in brain
How common is Tay-Sachs?
1 in 25 (Ashkenazi)
1 in 250 (General population)
How are newborns screened?
Clinical examination
Hearing
Blood spot
Why are babies screened?
Early detection
Early treatment
Reduce anxiety over symptoms
What are babies screened for?
PKU Congenital hypothyroidism Sickle cell CF MCADD Homocysteinuria Isovaleric acidaemia Maple syrup urine disease
How common is Phenylketonuria?
1 in 10,000
How is PKU carried?
Recessive condition
What is PKU?
Babies unable to break down Phenylalanine
How does untreated PKU present?
Irreversible mental disability
How is PKU treated?
Diet control by 21 days old
How common is Congenital Hypothyroidism?
1 in 4000
How does untreated Congenital Hypothyroidism present?
Serious permanent physical and mental disability
How is Congenital Hypothyroidism treated?
Levothyroxine by 21 days of age
How common is Medium chain Acyl-CoA Dehydrogenase Deficiency MCADD?
1 in 10-20,000
How is MCADD passed?
Recessive inherited condition
What is MCADD?
Babies cannot break down fat to make energy
How does MCADD present?
Serious symptoms in babies that are ill or not feeding
When are MCADD typically present?
14 months
How is MCADD treated?
Prevent metabolic crisis Avoid fasting Monitor meal frequency IN EMERGENCY: - Glucose polymer - IV dextrose
