Genomics, genetics and large animal Flashcards

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1
Q

Horse genome project done in

A

1995

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2
Q

Genetics

A

monogenic disorder

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3
Q

Genomics

A

polygenic disorders

  • specific disease-causing mutations
  • normal physiology
  • evolution of the horse
  • conservation medicine
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4
Q

Hyperkalemia periodic paralysis (HYPP)

A

QH and QH related horses

  • impressive founder stallion
  • skeletal muscle
  • autosomal co-dominant inheritance
  • ECA 11, SCN4A gene (voltage-gated Na Channel)
  • missense mutation
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5
Q

Sodium channel defect in HYPP caused by

A

altered alpha subunit

C to G substitution

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6
Q

What happens with the Na channels in HYPP

A

Na-channel don’t depolarize after stimulation- but stays open leading to continuous depolarization
Na-intracellular
K-extracellular
potassium sensitized - increased extracellular K+ lowers muscle membrane threshold potential

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7
Q

When do you see a paralytic attack in HYPP

A

inactivation of normal Na channels
loss of electrical excitability
paralytic attack

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8
Q

HYPP signs

A

episodic myotonia, muscle fasciculations, 3rd eyelid prolapse, weakness, respiratory distress, recumbency
Asymptomatic, daily episodes, death
hyperkalemia

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9
Q

HYPP therapy

A

establish and ensure normokalemia
drive K+ intracellular (syrup, glucose, insulin)
K+ excretion (acetazolamide, furosemide)
Dietary K+ restriction

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10
Q

Polysaccharide storage myopathy

A

autosomal dominant inheritance

  • GYS1 on ECA 10
  • gain of function dysregulation of glycogen synthesis
  • type 1 PSSM - QH breeds, draft horses, warmblood horses
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11
Q

PSSM physiology

A
  • PSMM horses remove sugar from the blood stream and transported into their muscle at a faster rate and make more glycogen than normal horses
  • PSSM very sensitive to insulin beginning as early as 6 months of age
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12
Q

Overactive enzyme in PSSM horse is

A

glycogen synthase

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13
Q

PSSM signs

A

vary in severity

  • stifness, pain, unwillingness to move, rhabdomyolysis, fasciculation’s, weakness, gait abnormalities and recumbency
  • muscle soreness, reluctance to engage the hind quarters muscle atrophy, and weakness
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14
Q

PSSM type 1 diagnosis

A

genetic testing available

Amylase resistant PAS within muscle biopsy tissue

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15
Q

PSSM therapy

A
acute
-rest
-fluid
-tranquilizers
-NSAIDs
Management
-diet low in soluble carbs
-fat supplementation
-regular exercise regimen 
-avoid stall confinement
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16
Q

PSSM type 2

A
  • abnormal glycogen staining in muscle biopsies
  • No specific genetic test for type 2 PSSM
  • therapy same as PSSM type 1
17
Q

HERDA

A
  • hyperelastosis cutis
  • derm condition in QH and related crosses
  • autosomal recessive
  • missense mutation, exon 1, cyclophilin B gene, ECA 1
18
Q

HERDA signs

A
  • appear age 1-1.5
  • excessive elasticity and fragility of the skin
  • hematomas, chronic secondary infections, abscesses and scarring
  • mare can carry pregnancy and foal out normally
19
Q

Ileocolonic aganglionosis (lethal white syndrome)

A
  • melanocytes and meteoric gangliocytes from the neural crest migrate to the skin and GI tract
  • TC to AG dinucleotide substitution endothelium receptor B gene, ECA
  • Homozygotes : migration failure
  • Heterozygotes: partial migration failure= white coat but functional peristalsis
20
Q

Polygenic diseases of the domestic horse

A
  • RAO
  • equine metabolic syndrome
  • guttural pouch tympany
  • genetic susceptibility to infectious diseases
  • orthopaedic disease
21
Q

Breed management considerations

A

Dominant traits
-propagation of the mutation results in affected animals rather silent carriers
-humane concerns
Delayed-onset recessive diseases
-risk of repeated rebreeding
Recessive trait
-unchecked breeding result in spreading undesirable allele
Polygenic disease management very difficult

22
Q

What types of disorders are expected to increase in bovine?

A

Autosomal recessive disorders

23
Q

Autosome recessive disorders in bovine

A
  • syndactyly- mobility issues, unthrifty
  • chondrodysplasia - varying degree 1,2,3
  • weaver
  • spinal dysmyelination - swiss brown
  • limber leg - jersey
  • spinal muscular atrophy (SMA)
  • rectovaginal constriction (RVC)
  • BLAD
  • DUMP
  • CVM
24
Q

Susceptibility to scrapie is?

A

genetically determined

25
Q

Susceptibility determined by?

A

three polymorphic AA codons at positions 136, 154 and 171in the prion protein

26
Q

Which sheep are most resistant to scrapie?

A

ARR/ARR

VRQ/VRQ, VRQ/ARQ, ARQ/ARQ genotypes most susceptible