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Molecular Medicine > Human Genetics > Flashcards

Human Genetics Flashcards

0
Q

Limitations of cytogenetics

A
  • only large abnormalities seen
  • labour intensive
  • specially trained staff
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1
Q

Reasons for cytogenetics referral

A

Infertility
Recurrent miscarriage
Primary and secondary amenorrhea
Amniotic fluid for advanced maternal age

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2
Q

4 main samples used in cytogenetics

A
  • blood
  • amniotic fluid
  • chorionic villus
  • bone marrow
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3
Q

3steps in the sample processing

A
  • culture
  • harvest
  • analysis
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4
Q

What is used to arrest cells in metaphase?

A

Colcemid

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5
Q

What does the potassium chloride do?

A

Hypotonic, so cells swell

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6
Q

Name 6 main types of structural chromosome abnormalities

A
  • deletion
  • ring chromosome
  • duplication
  • isochromosome
  • inversion
  • translocation
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7
Q

Two types of deletion

A
  • terminal

- interstitial

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8
Q

Types of staining

A
  • Giemsa banding
  • reverse banding
  • telomeric banding
  • centromere banding
  • NOR banding
  • quinacrine banding
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9
Q

4 things needed to name a band

A
  • chromosome number
  • arm symbol
  • region number
  • band number within that region
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10
Q

Use of FISH

A
  • microdeletions/duplications
  • aneuploidy
  • haematological disorders
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11
Q

Why is FISH useful for blood samples?

A
  • rapid, specific and accurate
  • not necessary to have good metaphases
  • able to combine several techniques and detect different nucleic acid targets in the same preparation
  • greater number of signals can be counted
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12
Q

Advantages of using FISH for haematological disorders

A
  • can detect a number of translocations
  • can be used to monitor minimal residual disease after treatment
  • can detect gene amplifications associated with an adverse prognosis for certain tumours
  • can be used to confirm engraftment
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13
Q

Describe a dual-fusion assay

A
  • utilizes large probes that span 2 break points
  • optimal for detection of low levels of nuclei possessing a simple balanced translocation
  • greatly reduces the number of normal background nuclei with an abnormal signal pattern
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14
Q

Describe break-apart assays

A
  • useful in the evaluation of genes known to have multiple translocation partners
  • differently coloured probes hybridize to targets on opposite sides of the breakpoint of the affected gene
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15
Q

Definition of monogenic disease

A

Diseases that result from modifications in a single gene occurring in all cells of the body

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16
Q

What may influence pedigrees in monogenic disorders?

A
  • reduced penetrance
  • variable expression
  • anticipation
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17
Q

Define reduced penetrance

A

When a person carrying a gene mutation manifests no signs

- AD ectrodactyly

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18
Q

Define variable expression

A

The way in which the disorder manifests differs between affected individuals
- tibial aplasia

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19
Q

Define anticipation

A

Presentation worsens with successive generations

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20
Q

What does MECP2 do?

A

It is a multifunctional epi genetic modulator

  • binds to forms of DNA that have been methylated
  • condenses the chromatin structure and form a complex with histone deacetylase or directly block TFs
  • May function as a transcriptional activator
  • highest levels of expression in neurons
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21
Q

What type of inheritance is Rett syndrome?

A

X linked dominant

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22
Q

Stages of female Rett syndrome

A
  • normal period
  • sudden decrease in interaction and slowing of progress
  • rapid developmental regression
  • deterioration slows, hand stereotypies, more interaction
  • loss of ambulation, spasticity
23
Q

Features of PPMX syndrome

A
  • severe ID and psychosis
  • parkinsonian features
  • pyramidal signs
  • macro-orchidism
24
Q

Features of MECP2 duplication syndrome

A
  • hypotonia
  • severe ID
  • epilepsy
25
Q

How to explain Rett syndrome

A
  • X inactivation pattern
  • depends on type of mutation (nonsense worse than missense)
  • depends of site of mutation
  • other genes can also be responsible
26
Q

Possible functional modifiers in Rett syndrome

A
  • alterations in the dopaminergic system
  • oxidative stress burden
  • mitochondrial dysfunction
27
Q

Types of microarrays

A
  • DNA
  • protein
  • tissue
  • cellular
  • chemical compound
  • antibody
  • carbohydrate
28
Q

Types of DNA arrays

A
  • expression chips
  • array CGH (comparative genomic hybridization)
  • mutation/ genotyping microarrays
29
Q

Features of stargardt macular degeneration

A
  • autosomal recessive
  • juvenile onset
  • mutations in ABCA4 gene
30
Q

Pros and cons of ABCR400 microarray

A
  • molecular diagnosis is unequivocal
  • raw microarray data cannot be delivered to patients without verification
  • chips only detect mutations at known points
31
Q

Definition of an adverse effect

A

Undesired events causing harm to patients, not by the underlying disease, but as a consequence of examination, treatment or care

32
Q

Definition of pharmacogenetics

A

The study of the role of inheritance in individual variation in response to xenobiotics

33
Q

Role enzymes in metabolizing drugs

A
  • modify most of the chemicals to which humans are exposed
  • convert them into more readily water-sol metabolites to be removed from the body
  • some reactions lead to formation of highly reactive intermediates
34
Q

What can genetic polymorphism lead to

A
  • abolished enzyme activity
  • reduced enzyme activity
  • increased enzyme activity
  • no change
35
Q

Aspects of pharmacokinetics

A
  • absorption
  • distribution
  • metabolism
  • excretion
36
Q

Aspects of pharmacodynamics

A
  • receptors
  • ion channels
  • enzymes
  • immune system
37
Q

Problems with poor metabolizers

A
  • too slow drug metabolism
  • too high drug conc at standard dose
  • high risk for adverse reactions
  • no response from pro drugs
38
Q

Problems with ultra metabolizers

A
  • too rapid drug metabolism

- no drug response at standard dose

39
Q

At what levels can genetic variation occur?

A
  • chromosomal
  • DNA sequence
  • nucleotide
40
Q

What is a haplotype?

A

A combination of alleles at adjacent locations on a chromosome that are inherited together

41
Q

Types of mutations

A
  • missense
  • synonymous
  • nonsense
  • sense
  • frame shift
  • mutation affecting polyA
  • splice site mutation
  • unstable mutations
42
Q

Factors affecting a pedigree

A
  • disease may not have shown phenotypically or person deceased prior to onset
  • spontaneous mutations
  • family size (small shows fewer)
  • variable gene expression
  • protective effect on mutation carrier
43
Q

Define detoxification

A

Conversion of lipid soluble chemicals into water soluble metabolites

44
Q

Define metabolic activation

A

Converting inert compounds into highly reactive molecules

45
Q

What is special about CYP?

A
  • single CYP can metabolize many compounds
  • many CYPs metabolize same compound at different sites
  • many CYPs metabolism same compound at same site at different rates
46
Q

Factors influencing drug metabolism

A
  • age
  • lifestyle
  • genetic polymorphisms
  • health status
47
Q

Definition of genetic polymorphism

A

The recurrence within a population of 2 or more genetic variants of a specific trait in such proportions that they cannot be maintained by simple mutation

48
Q

How are effects of polymorphisms measured?

A
  • phenotypically

- metabolic ratios

49
Q

Possible effects of polymorphisms

A
  • increased enzyme induction
  • altered enzyme activity
  • altered enzyme stability
  • altered enzyme specificity
50
Q

Genetic determinants of HIV progression

A
  • genetic diversity of HIV
  • host genetic susceptibility
  • host pharmacogenetics
51
Q

Why is pharmacogenetics considered in HIV?

A
  • the prevalence of toxicity
  • long term treatment
  • complexity of multi drug treatment
52
Q

Possible issues with pharmacogenetics

A
  • takes time to test
  • uptake by clinicians
  • clinical utility
53
Q

Define xenobiotics

A

A foreign compound/chemical found in an organism that is not normally produced or expected to be found in that organism

54
Q

Process of using a microarray

A
  • take a sample
  • isolate the mRNA
  • make DNA copies of mRNA and tag each sample with a different colour
  • apply labelled DNA to microarray
  • scan microarray
55
Q

What of expression chips do? (Microarray)

A

Determine the volume at which genes are expressed

56
Q

What do array CGHs do?

A

Determines genomic gains and losses (copy number variations)

Molecular Medicine (5 decks)

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