Complex Disease and Pharmacogenetics Flashcards

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1
Q

What are Mendelian traits?

A

Trait depending only on a single genes

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2
Q

What is an example of a Mendelian trait in humans?

A

ABO blood group (chromosome 9)

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3
Q

What are Complex traits?

A

Traits controlled by multiple genes and environment

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4
Q

What are the 2 types of traits?

A

Medelian and complex

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5
Q

What are 4 examples of complex traits?

A
  1. Height
  2. Weight
  3. Intelligence
  4. Blood pressure
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6
Q

What is a complex disease?

A

Disease arising from a combination of genetic, environmental, and lifestyle factors

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7
Q

What is an example of a complex disease?

A

CVD

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8
Q

Are Mendelian and complex traits definitively separate?

A

No - more like a scale from mendelian to complex

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9
Q

What are 3 factors contributing to traits?

A
  1. Genetics
  2. Epigenetics
  3. Environment
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10
Q

What are the 3 factors influencing SCD?

A
  1. Genetics —> β-globin chain point mutation
    —> other genes influence severity
  2. Epigenetics —> POFH (foetal Hb)
  3. Environment —> hypoxia (temp, altitude, pollutants, diet, smoking)
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11
Q

What are the 3 causes of phenotypic differences?

A
  1. Genetic differences
  2. Shared environment
  3. Unique environment
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12
Q

How can environmental effects on phenotypes be studied and why?

A

Twin studies
- Monozygotic —> 100% same genes —> test differences in environment
- Dizygotic —> share genes and environment

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13
Q

How can the heritability of phenotypes be studied?

A

Twin studies

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14
Q

What is concordance in genetics?

A

Whether a trait is shared?

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15
Q

Why is concordance not the same as heritability?

A

Influenced by environment

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16
Q

What are SNPs?

A

Single Nucleoside Polymorphisms
- Change in single nucleotide in genetic sequence

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17
Q

Do SNPs in non-coding regions have phenotypic effects?

A

Yes

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18
Q

What are association studies?

A

Examine the association between certain SNP and disease risk

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19
Q

What are the genetic causes of the aggression trait? (2)

A
  1. X-linked MAOA gene SNPs
  2. COMT/5HTT
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20
Q

What are the issues with association studies between SNPs and disease risk?

A
  1. Biased towards genes with known biological pathways
  2. May be differences in alleles unrelated to disease
  3. Limited to protein-coding regions
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21
Q

What are GWAS?

A

Genome-wide association studies
- Examine the association between SNPs in whole genome and disease risk

22
Q

How did GWAS change ideas about the aggression trait?

A

Found SNPs in genes for…
1. Neuronal excitability
2. Astrocyte differentiation
3. Post-synaptic density
4. Other proteins with unknown functions

23
Q

What are the 5 benefits of GWAS?

A
  1. Can identify SNP-variant associations
  2. Identify risk individuals
  3. Discover new biological mechanisms
  4. Informed drug discovery
  5. Identify ethnic differences
24
Q

What are the 4 limitations of GWAS?

A
  1. Further testing required to identify causal variants
  2. Can’t identify all heritability
  3. Won’t detect rare variants (won’t meet threshold)
  4. Doesn’t consider environmental influences
25
Q

How do most GWAS work?

A

Array panels —> detect common variants and omit rare

26
Q

What is the difference between GWAS and WGS?

A

WGS —> scrutinise entire genome —> see all SNPs

27
Q

What type of genome study are we moving towards?

A

WGS

28
Q

What is pharmacogenomics?

A

Study of variability in drug response due to genetic differences

29
Q

What are the aims of pharmacogenomics?

A

Improve drug therapy and prescribing

30
Q

How do genes affect drug effects? (2)

A
  1. Drug toxicity
  2. Drug efficacy
31
Q

Why can variation in drug-related genes not be observed through clinical trials alone?

A

Variation too rare

32
Q

What are the 5 steps of drug action in the body?

A
  1. Absorption
  2. Activation
  3. Target
  4. Effect
    or
  5. Inactivation
  6. Excretion
33
Q

What is pharmacokinetics?

A

Studies what the body does to the drug

34
Q

How are the majority of drugs administered and absorbed?

A

Orally —> small intestine

35
Q

What do drugs contain for absorption?

A

Specific transporter proteins

36
Q

How do varying combinations of drug transporter proteins affect absorption?

A

Increase absorption or enhance removal

37
Q

What is an SNP affecting drug absorption?

A

P-gp SNP affect digoxin/fexafenodine

38
Q

How does a P-gp SNP affect digoxin/fexafenodine effect?

A

Decrease

39
Q

How does drug metabolism influence a drug’s effect?

A

Activate/inactivate drug

40
Q

What is an example of drug metabolism effecting drug effect?

A

Ethanol metabolism

41
Q

How do SNPs influence alcohol’s effect?

A

Influence enzyme activity

42
Q

What is a prodrug?

A

Pharmacologically inactive till metabolised in body

43
Q

What is an inactive drug called?

A

Prodrug

44
Q

Which gene is involved in the metabolism of many drugs?

A

CYP2D6

45
Q

How does inheritance of CYP2D6 allelic variants effect the effect of drugs like codeine? (4)

A
  1. 2 active alleles —> ultra rapid metaboliser —> too much effect
  2. 1 fully active allele —> extensive metaboliser —>
  3. 1 reduced function allele —> intermediate metaboliser
  4. 2 non-functional alleles —> poor metaboliser —> too little effect
46
Q

What are the 4 targets of most drugs?

A
  1. Receptors
  2. Enzymes
  3. Ion channels
  4. Transport proteins
47
Q

Which drugs are used in hypertension treatment?

A

β-blockade

47
Q

What is the target of β-blockades?

A

β1 receptor in heart

48
Q

How do SNPs affect β-blockade action?

A

Decrease receptor activation

49
Q

How do β-blockades work?

A
  1. Slow heart rate
  2. Contractions weaker