Genetics Lecture Flashcards

1
Q

4 reasons for referral to genetics

A
  • FHx of genetic conditions
  • Diagnosis of genetic conditions
  • Managements of genetic conditions
  • Genetic counselling (aid decision making, increase understanding)
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2
Q

2 broad categories of pregnancy testing/screening

A
  • Targeted

- Whole population

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3
Q

6 types of genetic screening

A
  • Antenatal
  • Neonatal
  • Child
  • Adult
  • Pre-pregnancy
  • In maturity
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4
Q

4 pregnancy related genetics screening

A
  • Chorionic villus sampling
  • Amniocentesis
  • Pre-implantation genetic diagnosis
  • Non-invasive prenatal testing
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5
Q

Describe amniocentesis

A

-Amniotic fluid is withdrawn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)

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6
Q

Describe chorionic villus sampling

A

Biopsy of chorionic villus gives next day karyotype (8-10 weeks)

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7
Q

Risk of miscarriage associated with amniocentesis + chorionic villus sampling

A

0.5-1%

Chorionic villus sampling has > risk than amniocentesis

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8
Q

Main difference between chorionic villus sampling and amniocentesis

A
  • 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
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9
Q

Describe duchenne muscular dystrophy

A
  • X-linked
  • Fatal early in adult life
  • Carrier testing (prenatal and pre-implantation diagnosis)
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10
Q

Describe the screening for down syndrome

A
  • 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)
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11
Q

4 common recessive disorder that raise concern

A
  • Cystic fibrosis (n. Europe)
  • Sickle cell disease (Africa)
  • Thalassaemia (Mediterranean, Asia)
  • Breast/ovarian cancer BRCA1
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12
Q

3 carrier testings available by targeted testing in the UK

A
  • CF mutation analysis (80-90% sensitive)
  • Haemoglobinopathy
  • Tay-sachs enzyme activity (disease that progressively destroys neurons)
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13
Q

Describe Tay-Sachs disease

A
  • 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
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14
Q

3 newborn screenings

A
  • Clinical exam
  • Hearing
  • Blood spot
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15
Q

3 reasons to screen babies

A
  • 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
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16
Q

6 things that babies are screened for

A
  • Phenylketonuria (PKU)
  • Congenital hypothyroidism (CHT)
  • Sickle cell disorders (SCD)
  • Cystic Fibrosis (CF)
  • Medium chain acyl -CoA (MCADD
  • Maple syrup urine disease

And more

17
Q

Describe PKU

A
  • Unable to breakdown phenylalanine (amino acid)
  • Untreated babies develop serious, irreversible mental disability
  • Early treatment with a strictly controlled diet prevents disability
  • Treatment should begin by 21 days of age
18
Q

Describe CHT

A
  • Don’t have enough thyroxine
  • Untreated babies get serious, permanent, physical and mental disability
  • Early treatment prevents disability
  • Treatment should begin by 21 days of age
19
Q

Treatment for CHT

A

Thyroxine tablets (start by 21 days of age)

20
Q

Describe MCADD

A
  • Can’t easily breakdown fat to make energy
  • Serious, life-threatening, symptoms can occur quickly if babies not feeding or unwell
  • Mean presentation age 14 months
  • 25% mortality rate
  • Treatment to prevent metabolic crisis (avoid fasting + monitor frequency of meals)
21
Q

Emergency treatment for MCADD

A

Glucose polymer (maxijul) + IV dextrose

22
Q

Describe CF

A
  • Defect in cellular transport
  • Lung infections (acute/chronic)
  • Pancreatic insufficiency-
23
Q

Diagnosis of CF

A
  • Immunoreactive trypsin (1st 6 weeks)
  • Sweat test
  • Genotyping
24
Q

Describe SCD

A

-Abnormal haemoglobin
-Sickling
Pain+++
Cold
Dehydration
Infections
Jaundice
Stroke
Leg ulcers
?eye + kidneys?