Genetics

Question 1

What are the reproductive choices with regard to genetics?

Answer 1

• Nothing/? test at birth
• Chorionic villus sampling
• Amniocentesis
• Pre-implantation genetic diagnosis
• Adoption
• Gamete donation
• Non-invasive prenatal diagnosis/testing

Question 2

When would chronic villus sampling, amniocentesis or non invasive prenantal testing be used?

Answer 2

When there is a family history

Question 3

What are the features of Duchenne muscular dystrophy and how is it tested for?

Answer 3

• X linked
• Fatal in early adult life
• Carrier testing
• Prenatal diagnosis
• Pre-implantation diagnosis

Question 4

How is Down syndrome screened?

Answer 4

• Maternal age
• Triple screening
• CUBS screening
• Selection for amniocentesis
• Free fetal DNA (currently only private)

Question 5

Name some common recessive disorders that raise screening issues

Answer 5

• CF
• Sickle cell disease
• Thalassaemias
• Ashkenazi
• Tay-Sachs disease
• Breast/ovarian cancer BRCA1`

Question 6

Which carrier testing is available?

Answer 6

• CF mutation analysis
• Haemoglobinopathy
• Tay-Sachs

Question 7

How is cystic fibrosis diagnosed?

Answer 7

• Immunoreactive trypsin (first 6 weeks)
• Sweat test
• Genotyping

Question 8

What are the symptoms of sickle cell disorders?

Answer 8

• Pain
• Cold, dehydration and infections
• Jaundice, stroke, leg ulcers, eyes and kidneys
• Anaesthetic issue

Question 9

What are the features of Tay-Sachs disease?

Answer 9

• Progressive lysosomal storage disease
• hex-A deficiency results in the build up of lipid GM(2) esp. in nerve cells in the brain
• Normal development until six months and then progressive deterioration
• Usually fatal by 3-5yrs
• More common in Ashkenazi Jews

Question 10

How are newborns screened?

Answer 10

• Clinical examination
• Hearing
• Blood spot

Question 11

What are newborns screened for?

Answer 11

• PKU
• Congenital hypothyroidism
• Sickle cell disorders
• CF
• MCADD
• Homocysteinuria
• Isovaleric acidaemia
• Maple syrup urine disease
• Glutaric aciduria type 1

Question 12

What is PKU and how is it treated?

Answer 12

• Recessive condition
• Babies with the condition are unable to break down phenylalanine
• Untreated babies develop, serious, irreversible, mental disability
• Early treatment with a strictly controlled diet prevents disability

Question 13

What causes congenital hypothyroidism and how i it treated?

Answer 13

• Not enough thyroxine
• Untreated it causes serious, permanent physical and mental disability
• Early treatment with thyroxine tablets prevents disability

Question 14

What are the features of MCADD and how is it treated?

Answer 14

• Recessive condition
• Babies with MCADD cannot easily break down fat to make energy for the body
• Life threatening quickly in babies not feeding well or inwell
• Treatment: avoid fasting and monitor frequency of meals
• Emergency regime: glucose polymer and IV dextrose