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EXAM > Genetics 1.5 > Flashcards

Genetics 1.5 Flashcards

1
Q

Genetic technique that detects DNA?

A

Southern blotting

SNoW DRoP

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2
Q

Genetic technique that detects RNA?

A

Northern blotting

SNoW DRoP

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3
Q

Genetic technique that detects proteins? Example?

A

Western blotting
SNoW DRoP
e.g. confirmatory HIV test

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4
Q

Genetic technique that detects Ag & Ab?

Example?

A

ELISA
e.g. initial HIV test
Colour-changing enzyme attached to Ab, changes colour if Ag is detected. Enzyme attached to Ag if vice versa

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5
Q

2 complicating factors of Autosomal dominant inheritance?

A
  1. Non-penetrance (normal phenotype i.e. no Sx/Sx despite abnormal gene) e.g. 40% otosclerosis
  2. Spontaneous mutation (in one gamete e.g. 80% people with achondroplasia have unaffected parents)
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6
Q

Commonest congenital infection in UK

A

CMV

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7
Q

Characteristic features of Rubella?
(eyes, ears, heart)
Other features?

A
  1. congenital cataracts, glaucoma
  2. sensorineural deafness
  3. congenital heart disease e.g. PDA
    Others: growth retardation, hepatosplenomegaly, skin purport, salt & pepper chorioretinitis, microphthalmia, cerebral palsy
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8
Q

Types of Acyanotic congenital heart disease

A 
VSD (most prevalent)
ASD (present later, Dx in adults)
PDA
coarctation of Aorta
Aortic valve stenosis
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9
Q

Types of Cyanotic congenital heart disease

A

Tetralogy of fallot (commonest, present 1-2months)
Transposition of GA (present at birth so commoner then)
Tricuspid atresia
Pulmonary stenosis if severe

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10
Q

Conditions with X-linked Dominant inheritance

ARD

A

Alport’s syndrome (10-15% auto recessive)
Rett syndrome
Vitamin D resistant rickets

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11
Q

Who is affected in X linked recessive conditions?
Exception to this?
Who are the carriers?

A

Males are affected
Turner’s syndrome only one X chromosome therefore will be affected
Heterozygous females are carriers, unaffected. There male children have 50% chance of inheriting the gene therefore 50% chance of being affected

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12
Q

Genetics of William’s syndrome

A

Neurodeveopmental disorder caused by a micro deletion on chromosome 7
(contains elastin gene)

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13
Q

Features of William’s syndrome

neuro, development, biochem, heart

A

LD, friendly & social
Short stature, elif-like facies
Transient neonatal high Ca++
Supravalvular aortic stenosis

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14
Q

Dx William’s syndrome

A

FISH studies

fluorescent in-situ hybridisation

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15
Q

Genetics of Turner’s syndrome

A

Chromosomal disorder in 1/2500 females
1 sex chromosome or
deletion of short arm of 1 of the X chromosomes
(45, X or 45, XO)

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16
Q

Features of Turner’s syndrome?

heart, gynae, development, skin, autoimmune

A
  1. bicuspid aortic valve (15%), coarctation aorta (5-10)
  2. 1ry amenorrhoea
  3. webbed neck, short stature, shield chest, widely spaced nipples, high-arched palate, short 4th metacarpal
  4. neonatal feet lymphoedema, cystic hygroma, multiple pigmented naevi
  5. Inc incidence of AI disease esp thyroiditis, & Crohn’s
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17
Q

What are tumour suppressor genes

A

Normally control cell cycle
Loss of function = inc risk cancer
BOTH alleles mutated before cancer occurs

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18
Q

p53 - which chromosome?
ass cancers?
role in cell cycle?

A
  • chr 17p
  • many cancers e.g. breast, colon, lung
    Li-Fraumeni syndrome
  • prevents entry into S phase until DNA has been checked & repaired; also regulator of apoptosis
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19
Q

APC ass cancer

A

colorectal

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20
Q

Rb ass cancer

A

retinoblastoma

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21
Q

WT1 ass cancer

A

Wilm’s tumour

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22
Q

MTS-1, p16 ass cancer

A

melanoma

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23
Q

Genetics of Prader-Willi syndrome

A 
Genetic imprinting (phenotype depends if deletion occurs on gene inherited from father)
Absence of gene on long arm chr 15
- micro deletion of paternal 15q11-13 in 70%,
- maternal uniparental disomy of chr 15
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24
Q

Features of Prader-Willi syndrome

neurodevelopment, fert

A

hypotonia, dysmorphic features, short stature, childhood obesity, adolescence behavioural problems, LD
hypogonadism & infertility

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25
Q

Genetics of phenylketonuria

A
  • autosomal recessive disorder of phenylalanine metabolism

- usually defect in phenylalanine hydroxylase on chr 12 (converts phenylalanine to tyrosine)

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26
Q

Features of phenylketonuria

A

High levels of phenylalanine lead to:

  1. developmental delay, classically fair hair, blue eyes
  2. LD, seizures/infantile spasms
  3. eczema, ‘musty’ odour (phenyl acetate)
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27
Q

Dx phenylketonuria

A

Guthrie test
hyperphenylalaninaemia
phenylpyruvic acid in urine

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28
Q

What is PCR

A

Molecular genetic technique: sample DNA strand, 2 DNA oligonucleotide primers needed, complimentary to specific DNA sequences at either end of target DNA

  • 1 strand of sample DNA + 2 DNA primers + Taq (thermostable DNA polymerase)
  • heated -> denaturing = uncoiling of DNA -> cooled -> complimentary DNA strands pair (XS primer sequences pair with DNA preferentially) -> repeat cycle -> DNA doubles
29
Q

Reverse transcriptase PCR

A
  • amplifies RNA
  • reverse transcriptase converts RNA -> DNA
  • gene expression in the form of mRNA is analysed
30
Q

What is Li-Fraumeni syndrome

A

rare autosomal dominant
early onset of variety of cancers e.g. sarcomas, breast ca
p53 mutation

31
Q

3 processes by which photo-oncogenes (inv in cell growth & differentiation) becomes oncogenes?

A
  1. mutation (point)
  2. chromosomal translocation
  3. increased protein expression
32
Q

ABL is what cat of oncogene? ass cancer?

A

cytoplasmic tyrosine kinase

CML

33
Q

c-MYC is what cat of oncogene? ass cancer?

A

transcription factor

Burkitt’s lymphoma

34
Q

n-MYC is what cat of oncogene? ass cancer?

A

transcription factor

neuroblastoma

35
Q

BCL-2 is what cat of oncogene? ass cancer?

A

apoptosis regulator protein

follicular lymphoma

36
Q

RET is what cat of oncogene? ass cancer?

A

tyrosine kinase receptor

MEN II & III

37
Q

RAS is what cat of oncogene? ass cancer?

A

G-protein

many esp pancRAS

38
Q

erb-B2 (HER2/neu) is what cat of oncogene? ass cancer?

A

tyrosine kinase receptor

breast & ovarian

39
Q

Genetics of Noonan’s syndrome

A

autosomal dominant ass with normal karyotype

defect on chr 12

40
Q

Features of Noonan’s syndrome

turner’s, heart, face, blood

A
  1. webbed neck, wide nipples, short stature, pectus carinatum/excavatum
  2. pulmonary stenosis
  3. triangle face, low-set ears, ptosis
  4. coat problems e.g. factor XI deficiency
41
Q

dsDNA in mitochondria

A

encodes protein components of respiratory chain & some special types of rna

42
Q

histology in mitochondrial disease

A

muscle biopsy shows RED RAGGED fibres due to inc no of mitochondria

43
Q 
mitochondrial disease
inheritance?
who WILL get the disease?
who will NOT get the disease?
what is heteroplasmy?
A
  • maternal line of inheritance (sperm doesn’t contribute cytoplasm to zygote)
  • all children of affected females inherit
  • all children of affected males do NOT inherit
  • heteroplasmy: within tissue/cell there can be different mitochondrial populations. this is why there is poor genotype:phenotype correlation
44
Q

features of McCune-Albright syndrome

A

precocious puberty
cafe au last spots
polyostotic fibrous dysplasia
short stature

45
Q

Genetics of homocystinuria

A

rare autosomal recessive disease

  • cystathionine beta synthase deficiency
  • accumulation of homocysteine (then oxidised to homocystine)
46
Q

Dx of homocystinuria

A

cyanide-nitroprusside test (also +ve in cystinuria)

47
Q

Rx for homocystinuria

A

vitamin B6 (pyridoxine)

48
Q

Features of homocystinuria

skin/hair, msk, neuro, eye, blood

A
  1. fine fair hair, malar flush, livedo reticularis
  2. similar to Marfans
  3. may have LD, seizures
  4. downwards/inferonasal lens dislocation
  5. increase risk arterial & VTE
49
Q

Genetics of Fragile X syndrome?

A

trinucleotide repeat disorder

50
Q

Dx of Fragile X syndrome?

A
  • antenatal: chorionic villus sampling or amniocentesis

- analysis of no of CGG repeats using restriction endonuclease digestion and Southern blot analysis

51
Q

Features in Fragile X syndrome?

A

Female: range normal - mild (1 fragile 1 normal X chr)
Male:
- large low set ears, long thin face, high arched palate, macro-orchidism, hypotonia, mitral valve prolapse, LDs, autism is common

52
Q

Characteristic features of Toxoplasmosis?

others?

A
  • Cerebral calcification
  • Chorioretinitis
  • hydroCephalus
  • anaemia, hepatosplenomegaly, cerebral palsy
53
Q

Features of Wilm’s nephroblastoma?

A
  • abdo mass, flank pain, painless haematuria, anorexia, fever
  • 95% UL
  • 20% have mets (commonly lung)
  • usually under 5s
54
Q

Wilms’ nephroblastoma associations? (4)

A
  • Beckwith-Wiedemann syndrome
  • WAGR syndrome (aniridia, GU malform, mental retardation)
  • hemihypertrophy
  • 1/3 ass with loss-of-function mutation in WT1 gene on chr 11
55
Q

Management of Wilm’s nephroblastoma?

A

nephrectomy
chemo
RT if advanced
80% cure rate (good prognosis)

56
Q

Histology: epithelial tubules, areas of necrosis, immature glomerular structures, stroma with spindle cells, small cell blastomatous tissues resembling the metanephric blastema

A

Wilms’ nephroblastoma

57
Q

Classic definition of anticipation?

A

When unstable expansions (abnormal no of repeat trinucleotides) can enlarge leading to an EARLIER AGE OF ONSET in successive generations… often also with more severe phenotype

58
Q

Genetics of DiGeorge deficiency?

A
  • autosomal dominant
  • microdeletion on chr 22
  • 1ry immunodeficiency disorder caused by T-cell deficiency & dysfunction
  • aka velocardiofacial syndrome
  • 22q11.2
59
Q

Features of DiGeorge syndrome? CATCH22

variable presentation

A 
Cardiac abnormalities
Abnormal facies
Thymic hypo/aplasia
Cleft palate
Hypocalcaemia/hypoPTH (hypoplasia of parathyroid gland)
22 deletion

Also to rmr: at risk of viral & fungal infections; T-cell deficiency/dysfunction

60
Q

Genetics of Anderson-Fabry disease

A
  • X-linked recessive
  • Alpha-galactosidase A deficiency (normally responsible for breakdown of globotriaosylceramide)
  • Leads to abnormal deposits of globo… (fatty substance) that accumulate in BV walls leading to narrowing
61
Q 
Features of Anderon-Fabry disease?
MSK
heart
kidney
skin/eye
A
  • limb pain/paraesthesia esp in childhood, sensory neuropathy, Raynaud’s disease
  • early CVD, cardiac arrhythmias, cardiomyopathy
  • nephrotic syndrome: proteinuria
  • angiokeratomas, anhidrosis, cornea verticillata
62
Q

Genetics of Alkaptonuria (ochronosis)

A
  • rare autosomal recessive disorder of phenylalanine & tyrosine metabolism caused by a lack of homogentisic deoxygenate (HGD) leading to build-up of toxic homogentisic acid
  • kidneys filter this acid (hence black urine), but eventually it accumulates in cartilage etc
63
Q

Features of Alkaptonuria

A
  • generally benign & often aSx however
  • pigmented sclera
  • black urine if left exposed to air
  • intervertebral disc calcification -> back pain
  • renal stones
64
Q

Treatment of Alkaptonuria

A
  • high-dose vitamin C

- dietary restriction of phenylalanine & tyrosine

65
Q

Examples of trinucleotide repeat disorders (think neuro)

A 
Fragile X
Huntington's
myotonic dystrophy
Friedrichs ataxia
spinocerebella ataxia
spinobulbar muscular atrophy
dentatorubral pallidoluysian atrophy
66
Q

What is Ebstein’s anomaly?
Potential cause?
2 associations?

A

congenital heart defect characterised by low insertion of the tricuspid valve -> large atrium & small ventricle = ‘atrialisation’ of the RV

  • lithium exposure in-utero
    1. WPW syndrome
    2. tricuspid incompetence (PSM, giant V waves)
67
Q

Genetics of familial hypercholesterolaemia?

A

autosomal Dominant 1/500 people

gene mutation encoding LDL-receptor protein

68
Q

A primary immunodeficiency disorder caused by T-cell deficiency and dysfunction?

A

DiGeorge syndrome

  • microdeletion syndrome
  • therefore at inc risk of viral & fungal infections
69
Q

Autosomal dominant conditions

A 
achondroplasia
acute intermittent porphyria
adult polycystic kidneys
antithromb III deficiency
Ehlers-Danlos
Gilberts
familial adenomatous polyposis
hereditary haemorrhagic telangiectasia
hereditary spherocytosis
hereditary non-polyposis colorectal carcinoma
Huntington's disease
hyperlipidaemia type II
hypokalaemia periodic paralysis
malignant hyperthermia
Marfans
myotonic dystrophy
neurofibromatosis
Noonan syndrome
osteogenesis imperfecta
Peutz-Jeghers syndrome
retinoblastoma
Romano-ward syndrome
tuberous sclerosis
von Hippel-Linday sundrome
von Willebrands disease

EXAM (21 decks)

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