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RCPCH TAS/ AKP > Genetics > Flashcards

Genetics Flashcards

1
Q

Genetics and presentation of Russell-Silver Syndrome

A

Imprinting disorder. Maternal uniparental disomy Ch. 7. Reciprocal Beckwith-Wiedeman. Inherited from Father.
- Growth restriction
- Asymmetrical height
- Thin
- Triangular face
- Clinodactyly (curved)

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2
Q

Genetics and presentation of Turner’s Syndrome

A

45, XO
- Short
- Short 4/5th metacarpal
- CHD - Coarctation of aorta
- Cubitus valgus (arm bend out)
- Micrognathia
- Neck webbing
- Low hairline
- Wide spaced nipples, shield chest
- Renal (horseshoe)/ ear anomalies
- Infertility
- Lymphoedema as baby / hydrops

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3
Q

Management Turner’s

A

12-15y GH / oestrogen
Vit D / calcium - prevent OP

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4
Q

Genetics and presentation of Noonan’s Syndrome

A

Autosomal dominant condition affecting RAS / MAPK
- Short, webbed neck (look similar to Turner’s)
- Scoliosis
- Low set ears, hypertelorism
- CHD - RV outflow obstruction. pulmonary stenosis, hypertrophic cardiomyopathy
- Pectus excavatum
- Mild LD
- Oedema dorsum of foot.

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5
Q

Genetics and presentation of achondroplasia

A

Autosomal dominant. Mutation FGFR3 (inhibits cartilege and bone)
Shortened proximal long bones
Disproportionate sitting / standing height
Large head / frontal bossing /flat nasal bridge

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6
Q

Genetics and presentation of Klinefelter’s syndrome

A

47, XXY
Additional SHOX gene. Tall stature
Gynaecomastia
Female pattern hair
Broad hips
High pitched voice
Female distribution of fat
GDD / LD
Usually infertile

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7
Q

Management Klinefelter’s

A

12y - Testosterone replacement –> secondary sexual characteristics, improved behaviour

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8
Q

Genetics and presentation of Sotos syndrome

A

Mutation NSD1 gene
LD
Large head
Facial features

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9
Q

Genetics and presentation of Beckwith-Wiedemann syndrome

A

Ch11p15 (growth regulatory region). Imprinting disorder. 50% due to reduced methylation.
Reciprocal to Russell-Silver. Inherited from mother.
Large tongue, coarse facial features
Ear creases
Umbilical hernia
Neonatal hypoglycaemia
NB monitoring renal Wilm’s and hepatic tumours

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10
Q

What can karyotyping test for?

A

Structural abnormalities in chromosomes

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11
Q

What can array CGH (microarray) test for?

A

Chromosome copy number variations, can look for microdeletions and duplications (not balanced eg Translocation)
Large DDx eg LD

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12
Q

What does FISH look for?

A

Copy number variants and structural rearrangment - follow up array detected abnrormalities

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13
Q

What can quantitive fluorescent PCR look for?

A

Rapid aneuploidy testing, follow up array detected abnormalities

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14
Q

What is Mosaicism?

A

2 cell lines with diff. no. of chromosomes –> milder

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15
Q

Mechanism of genetic changes in trisomies?

A

Most meiotic non-dysjunction (mostly maternal)
Unbalanced translocation
Mosaicism

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16
Q

Presentation of Patau

A

LBW
Cardiac - ASD, VSD, PDA, dextrocardia
Facial abnormalities eg cleft
Neuro
Omphalocoele
Polydactyly
Rocker bottom feet

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17
Q

Presentation of Edward Syndrome

A

Most due to meiotic non-dysjunction
Facies - low set ears, prominent occiput
Flexed, overlapping fingers
Rockerbottom feet, hammer toes
IUGR
Cardiac - ASD, VSD, coarctation
Renal agenesis
Neuro

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18
Q

Clinical features of Down’s syndrome

A

IUG
Hypotonia
Upslanting palpebral fissures
Brachycephaly
Low set ears
Flat nasal bridge
Large protruding tongue
Single palmar crease
Brushfield spots
Sandal gap
Duodenal atresia
AVSD

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19
Q

Elements of combined screening test

A

10-14 weeks
Nuchal translucency
High beta-HCG
Low PAPP-A

20
Q

Elements of quadruple test

A

Beta-HCG - high
Inhibin-A - high
AFP - low
Oestriol - low

21
Q

When can invasive testing be done in pregnancy?

A

CVS 10-15 weeks
Amnio 15-20 weeks
Both 1% risk miscarriage

22
Q

Genetics and features of Di George Syndrome

A

22q11 deletion. Dominant. Usually de novo.
- Facial - long face, folded ears, narrow palpebral fissures, cleft
- Cardiac - TOF, truncus arteriosus, interrupted arch
- Hypocalcaemia, deficiency T cells (thymic hypoplasia)
- Renal tract anomalies
- LD / DD

23
Q

Genetics and features of William’s syndrome

A

7q11.23 deletion (elastin gene). De novo.
- Neonate: poor feeding, hypercalcaemia
- Facial - puffy eyes, long philtrum, stellate iris (lacy)
- LD
- Over chatty / friendly
- CHD - supravalvular aortic stenosis

24
Q

What can Sanger Sequencing be used for?

A

Small single gene defects

25
Q

What can targetted PCR / Southern Blotting be used for?

A

Trinucleotide repeats

26
Q

What can next generation sequencing be used for?

A

Sequencing gene / panel / exome / genome

27
Q

Genetics and presentation of Marfan’s

A

Dominant. Mutation FBN1 (fibrillin). Incomplete penetrance.
- Tall, large wing span
- Arachnodactyly
- Pectus excavatum
- Lens dislocation
- Aortic root dilatation

28
Q

Genetics and presentation NF1

A

Dominant. Loss of function NF1 (neurofibromin gene). Dx 2 or more of:
- 6 cafe-au-lait
- 2 neurofibroma
- Axillary / inguinal freckling
- Sphenoid wing dysplasia
- Optic nerve glioma
- 2 Lisch nodules (iris hamartoma)
- 1st degree relative FN1
Other features: renal artery stenosis, scoliosis, malignant neural sheath tumours

29
Q

Genetics and presentation of Tuberous Sclerosis

A

Dominant. Loss of function TSC 1/2 genes
- Cutaneous- Shagreen patches, ash leaf macules
- Prenatal rhabdomyoma
- Pulm / renal involvement

30
Q

Genetics of Cystic Fibrosis

A

Recessive. More W. Europe.
95% mutation to delta-F508 mutation Ch 7.
CFTR protein controls Chloride channels –> affects mucus.

31
Q

Features of CF

A

Frequent LRTI - pseudomonas
Meconium ileus
Malabsorption
Infertility

32
Q

Investigation and management of CF

A

Ix: High chloride on sweat test
DNA
D5 blood spot - high immunoreactive trypsinogen

Tx: ABx
Mucolytics
Creon

33
Q

Genetics and presentation of Fragile-X

A

X-linked recessive,
Triplet repeat in FMRI gene. >200 repeats = Sx.
Presentation: More males, LD, macrocephaly, mitral valve prolapse.
IX: Targeted genetic testing for expansion FMRI gene.

34
Q

Genetics and presentation of Rett Syndrome

A

X-linked dominant (usually lethal in males)
Loss of function MECP2 (specific sequence and copy numbers)
- Severe LD. Initially normal –> regression
- Slow head growth
- Midline hand movement
- Seizures

35
Q

Which is best tissue to test for mitochondrial disorders?

A

Muscles! Most mitochondria
Targeted sequencing, histology and electron microscopy

36
Q

Mechanism for imprinting

A
  • Methylation defect
  • Uniparental disomy - both copies from same parent. Expect offspring to be unaffected.
  • Uniparental deletion - deletion of imprinted region. 50% offspring.
  • Uniparental mutation of imprinted gene. 50% offspring.
37
Q

Genetic testing for imprinting disorders

A

1st line = methylation testing - PCR / MLPA
Micro satellite analysis - uniparental disomy
Microarray / MLPA (small area) - deletion testing
DNA sequencing - Point mutation / mutation of imprinted gene

38
Q

Genetics and presentation of Prader-Willi syndrome

A

Imprinting disorder 15q11 region. Inherited from FATHER. 70% deletion paternal copy.
Presents:
- Hypotonia
- Mild-mod LD
- SGA –> 12-18m obesity
- Hypogonadotrophic hypogonadism
Ix: Methylation testing –> microarray –> uniparental disomy testing

39
Q

Genetics and presentation of Angelman Syndrome

A

Imprinting disorder, 15q11, reciprocal to Prader-Willi.
Inactive UBE3A gene. Inherited from MOTHER.
Presentation:
- Severe LD 6-12m
- Ataxia
- Happy, smiley, hand flapping
- Microcephaly, wide mouth
- Seizures 80%
- Fair skin / hair
- Disordered sleep
IX: Methylation testing –> microarray –> uniparental disomy testing/ UBE3A sequencing

40
Q

Genetics and presentation of MEN2

A

Mutation in RET proto-oncogene. Autosomal dominant.
Associations – phaeochromocytoma, medullary thyroid cancer, parathyroid hyperplasia, adenoma-causing hyperparathyroidism

41
Q

Conditions associated with HLA-B27

A

Ankylosing spondylitis
Reactive arthritis
Anterior uveitis

42
Q

Genetics and presentation of Ehlers-Danlos syndrome

A

Mutation in COL5A1/2 genes –> defective collagen type V –> reduced collagen.
Present:
-Hyper-extensible skin
- Poor wound healing
- Skin fragility
- Joint hypermobility

43
Q

Blood group inheritance

A
  • ABO is controlled by gene with 3 alleles: i (O), IA, IB. One copy received from each parent. IA and IB dominant over i. Only someone with 2 copies of i will be O blood group. Co-dominance, if get IA and IB then will be AB. Eg parents A and B heterozygous –> ¼ chance of having a child with i (O blood group).
  • Rh – If both parents negative, child will be too. If one negative, and one positive, chance for either if heterozygous positive.
44
Q

What is high maternal AFP associated with?

A

Neural Tube Defects
Also: Multiple preg, abdo wall defects, Turner’s IUD

45
Q

What is low maternal AFP associated with?

A

Down’s syndrome

RCPCH TAS/ AKP (20 decks)

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