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Genetics Flashcards

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1
Q

What is chorionic villus sampling?

A

Sampling of the placenta
Occurs during the first trimester (usually weeks 10-13)
Relative risk of miscarriage is 1.5-2%

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2
Q

What is amniocentesis?

A

Sampling of the amniotic fluid which contain cells shed from the foetus skin
Usually occurs between weeks 16-18

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3
Q

Which inheritance pattern is not transmitted by males?

A

Mitochondrial Inheritance

Males do not transmit mitochondrial disorders because mitochondrial DNA is always exclusively maternally inherited. Paternal mDNA is eliminated from the egg in the early stages of embryogenesis

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4
Q

Which trinucleotide repeat relates to Fragile X?

A

CGG

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5
Q

Which trinucleotide repeat relates to Friedrichs Ataxia?

A

GAA

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6
Q

Which trinucleotide repeat relates to myotonic dystrophy?

A

CTG

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7
Q

Which trinucleotide repeat relates to spinocerebellar ataxia?

A

CAG

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8
Q

What are the main features of Fragile X?

A

Results from a loss of function mutation of FMR1 gene
Inherited in X-linked dominant fashion
Commonest cause of intellectual disability
Other features include - macroorchidism, large ears, high forehead, mitral valve prolapse and otitis media

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9
Q

Commonest cardiac problem in Noonan’s syndrome?

A

Pulmonary Valve Stenosis

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10
Q

Which genes are affected in Noonan’s syndrome?

A

Autosomal dominant inheritance
Mutation of PTPN11 gene on chromosome 12
Mutation of SOS1 gene on chromosome 2

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11
Q

How does William’s syndrome tend to present?

A

Over friendly personality
Supravalvular aortic stenosis
Facial features - thick everted lips, widely spaced teeth, upturned nose

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12
Q

Which genes are affected in Williams syndrome?

A

Microdeletion on 7q which encompasses for elastin gene

Hence testing for chromosome microarray will detect this

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13
Q

What are the features of DiGeorge Syndrome?

A

Microdeletion of chromosome 22q11.2
Features include:
Chromosome 22
Abnormal facies
Thymic aplasia
Cleft palate
Hypocalcaemia/ hypoparathyroidism

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14
Q

What are the features of Prader-Willi syndrome?

A

Causes include:
- Microdeletion of paternal chromosome 15q11.2-q13
- Maternal uniparentalidosomy of chromosome 15
- Imprinting defect

Features include:
- Compulsive over-eating
- Temper tantrums
- Mild intellectual disability

Diagnosis is by methylation studies

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15
Q

Outline which factors are affected in haemophilia?

A

Haemophilia A - factor VIII
Haemophilia B - factor IX

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16
Q

Which conditions represent maternal and paternal uniparental disomy of chromosome 15?

A

Maternal uniparental disomy of chromosome 15 - Prader Willi Syndrome
Paternal uniparental disomy of chromosome 15 - Angelmann Syndrome

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17
Q

What are the features of Duchenne’s Muscular Dystrophy?

A

X-linked recessive disorder
60% have the exon deletion or duplication of the dystrophin gene
All muscle affected - including cardiac
Typically die age 20-30 of cardiomyopathy
Deflazacort and prednisolone improve motor function - Deflazacort can cause increased risk of cataracts
Signs include calf hypertrophy and positive Gower’s sign (inability to get up from standing without use of hands)

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18
Q

What are the features of Edward Syndrome?

A

Intellectual disability
Microcephaly
Low set ears
Rocker bottom feet
Overlapping fingers
VSD

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19
Q

What are the features of Patau Syndrome?

A

Polydactyly (postaxial - on the ulnar side)
Cleft Palate
Microcephaly
Cutis Aplasia - area of baldness
PDA or VSD

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20
Q

What is trisomy 18?

Study These Flashcards
A

Edward Syndrome

21
Q

What is trisomy 13?

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A

Patau Syndrome

22
Q

What is 47, XXY?

Study These Flashcards
A

Klinefelters Syndrome

23
Q

What are the features of Klinefelters Syndrome?

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A

Tall
Gynaecomastia
Hypogonadism (small, firm testes)

Increased risk of breast cancer and testicular germ cell tumours

24
Q

What are the laboratory findings in Klinefleters Syndrome?

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A

High LH and FSH
High estradiol
Low serum testosterone

25
What is the treatment of Klinefelters syndrome?
Treatment with testosterone around the time of puberty (12 years old)
26
What is the treatment in Turners Syndrome?
Growth hormone Eostrogen treatment at puberty HTN treatment Thyroid replacement if required
27
What are the features of Noonan's syndrome?
Intellectual disability (25%) Bleeding disorders Pulmonary Valvular stenosis Small penis Cryptorchidism Features similar to Turners syndrome such as short stature, cubits values and short webbed neck
28
How is William's syndrome diagnosed?
FISH for the 7q11.23 elastin gene deletion
29
What are the features of William's syndrome?
Failure to thrive Hypotonia SUPRAVALVULAR AORTIC STENOSIS Cocktail party personality Stellate pattern of the iris Sensorineural hearing loss
30
What is WAGR syndrome?
Wilm's tumour (50% of cases) - haematuria, abdominal mass Aniridia Genitourinary Anomalies (hypospadias, cryptorchidism, gonadoblastoma) Retardation + intellectual disability
31
What genes are affected in Alagille syndrome?
Microdeletion of the 20p12 gene - JAG1 gene mutation
32
What are the features of Alagille syndrome?
Broadened forehead + pointed chin Jaundice (cholestasis due to bile duct paucity) Cardiac - peripheral pulmonary stenosis (systolic murmur) + ToF Butterfly hemivertebrae
33
How do you diagnose DiGeorge syndrome?
Array comparative genomic hybridisation - gold standard FISH - widely available and more affordable but can miss the diagnosis as it is a micro deletion
34
What are the features of cri-du-chat syndrome?
Moon face Flat nasal bridge Down-slanting palpebral fissures Microcephaly Strabismus Hypotonia -> poor feeding High pitched cry
35
What is the mutation causing cri-du-chat syndrome?
Deletion of 5p
36
What is the mutation causing achondroplasia?
Mutation in the gene for fibroblast growth factor receptor 3 (FGFR3) on chromosome 4 Autosomal dominant
37
What is the mutation causing Marfans syndrome?
Defect in FBN1 gene on chromosome 15q; fibrillin Autosomal dominant
38
What are the features of Marfan's Syndrome?
Dislocated lens Aortic dissection/ rupture of the aorta Scoliosis Long arms/ fingers Pectus excavatum (funnel chest) Pectus carinatum (pigeon breast) Tall and thin
39
What the diagnostic criteria make up the "Revised Ghent Criteria" used to diagnose Marfan syndrome?
Family History Aortic root dilatation Ectopia Lentísimas Systemic Score Points Identified FBN1 mutation
40
What mutations cause Ehlers-Danlos Syndrome?
Mutation of COL5A1 or COL5A2 genes (Collagen type 5 genes)
41
What mutations occur in Beckwith-Wiedemann Syndrome?
Abnormalities of the distal 11p->IGF2 (Over production of insulin like growth factor 2 which causes overgrowth of organs)
42
What are the features of Beckwith-Wiedemann Syndrome?
Neonatal period: - Severe hypoglycaemia - Omphalocele - Umbilical hernia - Large tongue (macroglossia) Hemi-hypertrophy Pits of the external ear High risk of development of Wilm's tumour (patients should have abdominal USS every 3 months until 3 years then every 6 months)
43
What is Klipple-Feil syndrome?
Due to a defect in formation of the segmentation of cervical vertebrae Features include: - Short neck or webbed neck - Low hairline - Associated with single kidney
44
What are the features of Treacher-Collins Syndrome?
Affects facial bones, ears and eyes Underdeveloped mandibular and zygomatic bones Conductive hearing loss Coloboma Aplasia of the lid lashes
45
What are the features of Waardenburg Syndrome?
Hair hypo pigmentation + premature greying of hair Abnormal pigmentation of the iris (both eyes can be different colours - heterocromia) Associated with hirschsprungs disease
46
What are the clinical features of Turner's Syndrome?
Webbed neck/ cystic hygroma BICUSPID AORTIC VALVE Short stature Wide carrying angle Short 4th and 5th metacarpal/tarsal Wide spaced nipples Horseshoe kidneys Lymphoedema at birth - resolves after several months
46
Which pharyngeal arches are affected in DiGeorge Syndrome?
Third and Fourth
47
What type of mutations is FISH genetic testing specifically used for?
Microdeletions NB: rare very small deletions may not be detected on FISH testing - use microarray testing in these cases
48
How does FISH testing work?
Detects a specific DNA sequence on a chromosome DNA probe containing a fluorescent probe detects specific chromosome - 2 signals is normal, 1 signal means a deletion

TAS Revision (14 decks)

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