Genetics

Question 1

When can genetic testing be carried out?

Answer 1

• antenatal
• neonatal
• child
• adult
• pre-pregnancy
• in maturity

Question 2

What are some genetic testing options in pregnancy?

Answer 2

Chorionic villus sampling
Amniocentesis
Pre-implantation genetic diagnosis
Gamete donation

Question 3

Describe autosomal dominant inheritance

Answer 3

Each child has 50% chance inheriting mutation

No “skipped generations”

Equally transmitted by men and women

Question 4

Describe screening for down syndrome

Answer 4

Maternal age
Triple screening
CUBS screening
Selection for amniocentesis

Free foetal DNA

• private @ £500
• coming to NHS

Question 5

What are some common recessive disorders?

Answer 5

N. Europe; cystic fibrosis

Africans; Sickle Cell Disease

Mediterranean, Asia; Thalassaemias

Breast/ovarian cancer; BRCA1

Question 6

Describe CF

Answer 6

Defect of cellular chloride transport

Meconium ileus

Lung infections; acute, chronic

Pancreatic insufficiency

Diagnosis; immunoreactive trypsin (first 6 weeks), sweat test, genotyping

> 1000 gene mutations cause disease

Question 7

Describe sickle cell disorders

Answer 7

Abnormal HB gene

Sickle commonest UK

Sickling

• pain +++
• cold, dehydration, infections
• jaundice, stroke, leg ulcers, eyes, kidneys
• African, Mediterranean, Middle-East, Indian
• Anaesthetic issues

Question 8

Describe Tay Sachs disease

Answer 8

Progressive, genetic, lysosomal storage

hex-A deficiency results in build up of lipid esp in nerve cells of brain

Baby usually develops normally until ~6months

Progressive neurological deterioration

usually fatal by 3-5years

Question 9

Describe newborn screening

Answer 9

Clinical examination
Hearing

Blood spot

Question 10

Why do we screen babies?

Answer 10

Enable early detection pre-symptomatic babies

Enable early treatment to improve health

Reduce anxiety caused by uncertainty over symptoms before clinical diagnosis made

Question 11

What do we screen babies for?

Answer 11

• phenylketonuria (PKU)
• Congenital Hypothyroidism (CHT)
• sickle cell disorders (SCD)
• Cystic fibrosis (CF)
• MCADD; medium chain acyl-CoA dehydrogenase deficiency

Question 12

Describe MCADD

Answer 12

Medium chain acyl-CoA dehydrogenase deficiency

Recessive inherited condition

Person has problems breaking down fat to use as an energy source

Serious life threatening symptoms can occur in babies not feeding well or unwell

Treatment to prevent metabolic crisis; avoid fasting and monitor meal frequency

EMERGENCY REGIME; glucose polymer and IV dextrose

Question 13

What is PKU?

Answer 13

Phenylketonuria

Affects ~1 in 10,000 babies in UK

Recessive; biochemical screen, carriers not identified

Cannot break down phenylalanine (AA in protein)

Untreated develop serious, irreversible mental disability

Early treatment with strictly controlled diet prevents

treatment should start by 21 days of age

Question 14

Describe congenital hypothyroidism

Answer 14

1 in 4000 babies UK

1 in 10 cases inherited; hormone test

Not enough thyroxine

untreated; serious, permanent physical and mental disability

Early treatment with thyroxine tablets prevents disability

Treatment should start by 21 days of age