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P Intergrated Y2 > GiM Lecture 1,2,3 > Flashcards

GiM Lecture 1,2,3 Flashcards

1
Q

Reasons for clinical genetics referrals

A

Child
Birth anomalies, dysmorphic features, learning difficulties

Adult
Diagnosis, predictive testing, carrier testing, family history, foetal loss/recurrent miscarriage

Pregnancy
genetic disorder, screening abnormality

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2
Q

What is genetic counselling

A

Education process to assist affected or at risk individuals understand the nature of genetic disorder, transmissions and available options

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3
Q

How are genetic diagnosis made

A

Family tree - pattern of inheritance
Physical examination
Genetic Tests - Chromosome, Genes

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4
Q

Testing For genetic disorders

  • Non genetic tests
  • Genetic tests
A

Blood tests

  • Enzyme assays
  • Inborn errors of metabolism

Haematology
-thalassaemia
X Rays
-Skeletal dysplasia

Genetic
Genomic architecture
-Cytogenetics
-Array based techniques
Gene faults
-Sequencing
-OLA assays
-MLPA tests
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5
Q

Advantages and disadvantages of genetic testings for disorders

A

Advantages

  • Early diagnosis
  • Early interventions
  • Carrier testing
  • Reproductive choices
  • Prenatal testing

Disadvantages

  • no treatment
  • does knowing help
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6
Q

What is Pharmacogenomics

A

Analysis of entire genomes of a group

aim to identify genetic factors influencing response to a drug

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7
Q

What is pharmacogenetics

A

Study an individuals genetic make up to predict drug response and guide prescription

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8
Q

What is Glevec

A

Treatment for CML (chronic myeloid leukemia)

Targeted at novel fusion protein which is the product of translocation in CML

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9
Q

What are contributions to human diseases

A

genetic

environmental

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10
Q

Define

- Multifactorial genetic disorder

A

the interaction of multiple genes (genetic predisposition) in combination with environmental factors eg type II diabetes, ischemic heart disease.

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11
Q

define

- single gene genetic disorder

A

a mutation in a single gene = Mendelian inheritance – AD, AR, XL eg cystic fibrosis

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12
Q

Define -

Chromosomal genetic disorder

A

an imbalance or rearrangement in chromosome structure eg aneuploidy, deletion, translocation

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13
Q

Define

- Mitochondrial genetic disorder

A

a mutation in mitochondrial DNA

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14
Q

Define

- somatic mutations

A

mutation(s) within a gene(s) in a defined population of cells that results in disease eg breast cancer

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15
Q

What are the single gene modes of inheritance

A

Autosomal Dominant
Autosomal Recessive
X-linked
Mitochondrial

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16
Q

What is Autosomal dominant inheritance

  • What does it mainly affect
  • give 3 examples of autosomal dominant conditions
A

A trait or disease runs from one generation to the next

Males and females equally affected

Offspring of affected person has a 50% (1 in 2) chance of inheriting the mutation

Structural proteins, receptors, transcription factors

Myotonic dystropy
Marfan Syndrome
Huntingdon Disease

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17
Q

Autosomal Dominant Inheritance

  • What genotype are those affected
  • What is the change off spring is
    a) affected
    b) unaffected
A 
Affected = 50% 
Affected = heterozygous

Unaffected - 50%
Homozygous

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18
Q

What is Penetrance?

- give example of a disease with 100% penetrance

A

The frequency with which a specific genotype is expressed by those individuals that possess it,
e.g huntingdons has 100% penetrance

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19
Q

What is expressivity

A

variation in expression - the extent to which a heritable trait is manifested by an individual

e.g. marfan - aortic dilation –> stretch marks

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20
Q

What is anticipation?

- two disease examples

A

the symptoms of a genetic disorder become apparent at an earlier age as it is passed from one generation to the next. In most cases there is an increase in the severity of symptoms too

  • myotonic dystrophy
  • huntington’s disease
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21
Q

Define

De Novo Mutation

A

new mutation that has occurred during gametogenesis or in early embryonic development.

22
Q

Explain Autosomal Recessive inheritance

  • give examples of autosomal recessive inheritance diseases
A
  • Disease seen in one generation
  • consanguineous relationship increases risk of disease offspring
  • relatives maybe carriers
  • affects M and F equally
  • Gene mutations not chromosomes
  • cystic fibrosis
  • metabolic disorders
  • haemachromatosis
  • sickle cell
23
Q

Autosomal Recessive inheritance

  • What genotype are affected
  • What risk of being affected
  • risk of being an unaffected carrier
A

Affected = homozygous or compound heterozgous
Affected = 25%
unaffected Carrier = 2/3
unaffected = 25%

24
Q

X linked inheritance

  • Explain
  • Example diseases
A

Males affected
Females - spectrum - unaffected –> fully
M usually more affected
Female transmission ONLY
Possible in
- Gene mutations, chromosome deletions and duplications

Duchenne Muscular Dystrophy
Fragile X syndrome
Red/green colour blindness
Haemophilia

25
Q

X linked inheritance - Carrier Mother

  • Affected Boy
  • Carrier Girl
  • Normal Boy
  • Normal Girl
A

25%

26
Q

X linked inheritance - affected father

  • daughters?
  • Sons?
A 
D = All carriers
S = unaffected - no male transmission
27
Q

X linked inheritance

Why can females have varying phenotypes

A

X inactivation
XL dominant vs XL recessive inheritance

CANNOT predict female phenotype in prenatal testing

28
Q

What is Lyonisation?

A
  • X- inactivation
  • One X chromosome in cells with XX is turned off.
  • Occurs in early embryogenesis
  • Most but not all inactivated X genes turned off.
29
Q

X inactivation and disease expression
What is skewed X inactivation?
What is tissue variability

A

Skewed = random preference for normal X chromosome to be inactivated over abnormal X

Tissue - Random prefernece for mutated X chromosome to be active in crucial tissue group

30
Q

X linked Dominant inheritance

  • Affects?
  • Who does Rett syndrome effect
  • Who does Fragile X syndrome effect
A

Males and females
Rett - lethal in M, phenotype only in F

Fragile X - M affected, F - spectrum

31
Q

X linked Recessive

  • affects?
  • are carrier girls affected?
A

Affects - males,
carrier females
can be affected F is homozygous

carrier girls - affected if x inactivation skews

32
Q

Mitochondrial Inheritance

  • explain
  • example
A
  • Maternally inherited diabetes and deafness
  • Rare , M = F affected
  • only 27 genes in mitchondrial DNA
  • always maternally inherited
  • affected mother = ALL offspring affected
  • affected father - no affect
33
Q 
Family trees
What does .... mean?
- Circle
- square
- diamond
- diamond crossed out
- triangle 
- triangle crossed out
- filled circle/square
- square/circle with dot
A
  • female unaffected
  • male unaffected
  • unknown sex
  • still born unknown sex
  • miscarriage
  • abortion
  • affected F/M
  • asymptomatic carrier
34
Q

What is the symbol for
- Consanguinity
How does it affect genetics

A

Double line between couple

  • blood relative
  • congenital birth defect 5-6% risk (pop normal = 2-3%)
35
Q

What is Polymerase chain reaction

A

In Vitro synthesis of large amounts of DNA

Oligonucleotides define boundaries of synthesis

DNA synthesized by DNA polymerase enzyme

1) Heat denaturation 94 degree
2) primer annealing 55 degree
3) primer extension 72 degree

Products separated by GEL electrophoresis and visualized with UV

36
Q

What can be determined by PCR

A

Presence/absence of something
- allele specific PCR

product size by gel electrophoresis

  • Oligonucleotide ligation assay
  • direct sequencing
37
Q

How does gel electrophoresis work

A

Electrical current
small products move towards +ve end
large products remain at -ve end

DNA is -ve charged therefore moves towards +ve

38
Q

What is the mutation for the most common inherited cause of deafness

A

Connexin 26

GJB2

39
Q

What can a delta35g assay show

A

accurate size analysis - can show single base deletions
- able to distinguish
hetero zygotes, homo zygotes, and normal

40
Q

What is Allele specific mutation
detection
- method
- use

A
  • distinguish between 2 alleles that differ by one nucleotide
    aka - Oligonucleotide Ligation Assay
  • allele specific primer- 3’ nucleotide base pair with changed nucleotide
  • reaction will not occur if base pair not perfect
  • able to tell abnormal from normal alleles
41
Q

How can Cystic fibrosis gene mutations be identified

A

Cystic Fibrosis genotyping assay

42
Q

What is Multiplex Ligation- dependent probe amplication analysis (MLPA)

A
  • detects chromosomal DNA copy number changes in multiple targets
43
Q

What is the amount of product from PCR proportional to?

A

the amount of target DNA present

44
Q

What are the problems with mutation anaylsis

A

gene might be too big for PCR
gene may be repetitive
GC rich regions are hard to PCR

45
Q

Souther Blotting is used for what?

A

Fragile X syndrome

DNA

46
Q

what is DNA sequencing

A

Detection of unknown mutations
= exact position of mutation
- type of mutation
uses specific PCR product as template

47
Q

What nucleotides are used in sequencing?

A

dNTP deoxyribose nucleotides

dideoxyNTP dideoxyribosenucleotides

48
Q

how do ddTTPs help with sequencing

A

stop chains continuing to grow
lots of chains different lengths
can read sequence by gel electrophoresis

49
Q

What is MEGF10 mutation screening

A

distinguish between different muscular dystrophies

50
Q

What is clonal sequencing

A

next generation
Illumina Method
Long PCR product covering gene
produces flow cell images

P Intergrated Y2 (13 decks)

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