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OD1 Semester 2 - Integrated Ophthalmic Sciences and Preclinical Optometry > Intro to genetics eye disease - week 3 > Flashcards

Intro to genetics eye disease - week 3 Flashcards

1
Q

List the 6 general patterns of Mendelian inheritance.

A
  1. Autosomal recessive
  2. Autosomal dominant
  3. x-linked recessive
  4. x-linked dominant
  5. codominant
  6. mitochondrial
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2
Q

Define Monogenic trait

A

A characteristic produced by a single gene or allele

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3
Q

Define Complex trait

A

A trait that does NOT follow Mendelian Inheritance patterns, is likely derived from multiple genes, and exhibits a large variety of phenotypes

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4
Q

How can glaucoma be inherited? (in terms of inheritance pattern)

A

Glaucoma can be inherited as a mendelian autosomal-dominant or recessive trait, OR as a complex multifactorial trait.

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5
Q

Explain the different frequencies and severities for monogenic and complex traits using glaucoma as an example

A

Mendelian inheritance i.e. monogenic traits (e.g. mutation in MYOC) will have the rarest frequency but the largest effect size

Complex traits are inherited through ‘modifiers’, which contribute to the disease (e.g. COL1SAT for glaucoma)

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6
Q

As an adult, what is the frequency and severity of the mutations in genes that modify SNPs? Give an example of one such gene

A

Common with low severity e.g. TMCO1

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7
Q

In the context of glaucoma, what traits are influenced by genes mutations that modify SNPs?

A

traits like IOP, corneal thickness that increase disease risk

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8
Q

Do genes mutations that modify SNPs always result in a disease?

A

No. e.g. High IOP doesn’t mean you have glaucoma. It just increases the risk

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9
Q

What proportion of STRAB patients have a family history of the condition?

A

~30%

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10
Q

Incidence of STRAB in general population

A

3%

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11
Q

What is the role of the genes associated with STRAB?

A

role in normal development of and/or connectivity of cranial motorneurons

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12
Q

Describe Congenital Nystagmus

A

Is an eye movement problem where the eye movement centres have lost control, and you get a ‘lateral jerk’

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13
Q

How many loci are associated with very high myopia? [must know]

A

18 loci

  • 9 autosomal dominant (AD)
  • 1 autosomal recessive (AR)
  • 2 x-linked recessive (XL)
  • 6 other loci
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14
Q

Which is the key gene that regulates lens development?

A

Pax6

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15
Q

Which gene leads to the development of lens crystallins?

A

CRY

  • cry = “cry”stallin (Cry Stalin)
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16
Q

What gene that controls gap junctions can cause a congenital cataract when mutated?

A

Cx43

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17
Q

Where are aquaporins found in the eye? [name 3]

A

ciliary epithelium, corneal epithelium, conjunctival epithelium

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18
Q

What mutations can cause congenital cataract? [4]

A

Mutations of genes that control:

  • lens development (Pax6)
  • lens crystallins (CRY)
  • gap junctions (Cx43)
  • aquaporins
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19
Q

Why are gap junctions important for optical clarity?

A

Important for communication between fibres and between lesn capsule and it’s external environment. Therefore important for ionic transport which is important to maintain clarity

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20
Q

Define coloboma

A

Failure of fissure to close/incomplete closure

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21
Q

Define aniridia

A

Absence of the iris

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22
Q

Name 2 gene mutations that are associated with intraocular coloboma and aniridia

A

Pax6 gene mutation at 11p1

WT1 mutation

23
Q

Name 3 genes assoc. with anopthalmia/microphthalmia

A
  • Pax6
  • OTX2
  • NDP
24
Q

Vaguely describe optic nerve hypoplasia in 4 words

A

Loss of O.N tissue

25
Q

List the risk factors of Optic nerve hypoplasia (ONH):

A
  • preterm birth
  • alcohol
  • quinine (for Malaria)
  • phenytoin (for seizures + cardiac problems)
  • Maternal diabetes
  • Congenital Cytomegalocirus (CMV) infection
  • LSD consumption
26
Q

Vaguely describe the roles of transcription factors assoc. with ONH

A

Any transcription factors that are critical to the development of the eye and nuerogenesis

27
Q

What is the role of the enzyme RPE65

A

RPE65 is essential for the recycling of the chromophore

28
Q

What types of gene abnormalities can lead to retinal degeneration?

A

Abnormality in any gene that drives what photoreceptors do can lead to retinal degeneration

29
Q

Name an example of retinal degeneration

A

Retinitis Pigmentosa

30
Q

Briefly describe what happens in Retinitis Pigmentosa when the photoreceptors die off

A

When photoreceptors die off, the RPE can also die off – leading to clumping of pigmentation in the retina

This pigmentation is known as ‘bony spicule’

31
Q

List the causes of Retinitis Pigmentosa (RP)? [7]

A

Mutations in proteins involved in:

  • Phototransduction cascade
  • Vitamin A metabolism
  • Signalling, cell-cell interaction or synaptic interaction
  • Trafficking of intracellular proteins
  • Maintenance of cilia
  • pH regulation (choriocapillaris)
  • Phagocytosis

Please vote soon to make Prasan President

32
Q

How long does the recycling process of retinol/retinal take in dark adaptation?

A

Around 30 minutes

33
Q

What condition do mutations in RPE65 lead to?

A

Leber’s Congenital Amaurosis (LCA)

34
Q

How many different gene mutations can cause LCA?

A

mutations in more than 12 genes

35
Q

How can we assess retinal function In Retinitis Pigmentosis subjectively and objectively?

A

Subjective:
- V.A, Contrast Sensitivity, Flicker Sensitivity, Dark Adaptation, Visual Fields

Objective:
- pupil responses, electrophysiology

36
Q

Explain how the electrodes work in EOG.

A

Put electrodes on the temples and one electrode in the middle. As your eye is moved from side to side, the electron current will change direction which will be picked up by the electrodes –> this current/change is driven by potassium through the RPE

37
Q

In which scenario does the RPE work harder: light or dark?

A

Dark. RPE works hard for recycling

38
Q

What is the Arden Ratio?

A

is the ratio of the light peak to dark, and is used to determine the normalcy of the results in EOG

39
Q

What values for Arden ratio are normal or abnormal? [own research]

A

Greater than 1.80 is normal
1.65 to 1.80 is subnormal
less than 1.65 is significantly subnormal

40
Q

What is the typical Arden ratio?

A

Normally greater 2.0

41
Q

Which type of retinal cell currents sum up, and which cancel?

A

Radial retinal cell currents sum up

Lateral currents cancel

42
Q

What are the 2 pathways that light induced extracellular current divides into?

A
  1. Internal (local) current

2. External (remote) current

43
Q

In ERG, which wave tells us about the muller cells?

A

The c wave

44
Q

In ERG, which wave is associated with off bipolar cells

A

The d wave

45
Q

In ERG, which wave is assoc. with on bipolar cells

A

The b wave

46
Q

In ERG, which wave is assoc. with photoreceptors and reduction in dark current?

A

The a wave

47
Q

Which retinal pathway do Amacrine cells belong to?

A

The Lateral pathway

48
Q

How does the lateral pathway interact with the through pathway?

A

Lateral pathway modifies the response of the through pathway. e.g. it’s involved in inhibition etc

49
Q

Which neurotransmitter is inhibitory GABA or GLUTA?

A

GABA

50
Q

Which neurotransmitter is excitatory GABA or GLUTA?

A

GLUTA

51
Q

Are amacrine cells glutaergic or gabaergic?

A

GABAergic

52
Q

How does the brightness of the test flash affect the amplitude of the ERG? How would describe this phenomenon

A

makes it bigger. This is a Dose response function

53
Q

What happens to the b-wave when you block glutamate?

A

It disappears

54
Q

Where do mutations occur to cause Lebers hereditary optic nerve atrophy?

A

mutations in mitochondrial dna

OD1 Semester 2 - Integrated Ophthalmic Sciences and Preclinical Optometry (49 decks)

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