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Phase 3 > Week 1 - Genetics > Flashcards

Week 1 - Genetics Flashcards

1
Q

Which gene is involved in Hungtinton disease?

A

Huntingtin (HTT)

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2
Q

How many CAG repeats in the Huntingtin gene is normal?

A

10-35

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3
Q

How many CAG repeats in the Hungtintin gene are associated with Huntington’s disease?

A

36-120

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4
Q

Which type of genetic transmission is susceptible to gene expansion during meiosis in Huntington disease?

A

Paternal

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5
Q

What is genetic antisipation?

A

Expansion of gene mutation during meiosis, leading to increased severity and age on onset in subsequent generations

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6
Q

How does a mutation in the huntingtin gene cause the symptoms of Huntington’s disease?

A

Gene codes for a polyglutamine tract

Expansion of tract causes insoluble protein aggregates which lead to neurotoxicity

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7
Q

What are the main symptoms of myotonic dystrophy?

A

Progressive muscle weakness in early adulthood
Myotonia
Cataracts

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8
Q

Which gene is mutation in myotonic dystrophy and what is the nature of the mutation?

A

DMPK gene

Unstable length mutation of CTG repeat in 3’ region (50 or more repeats)

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9
Q

Which type of transmission more commonly causes expansion in myotonic dystrophy?

A

Maternal

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10
Q

What effect does mutation of the DMPK gene have?

A

Indirect toxic effect upon spicing of other genes such as the chloride ion channel (causing myotonic)

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11
Q

What is a common complication of CF? (other than lung infections)

A

Exocrine pancreas insufficiency

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12
Q

How is CF diagnosed?

A

Screening of newborns (heel prick) by immunoreactive trypsin (IRT) level
DNA testing for CF mutations
Sweat testing for increased chloride concentration

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13
Q

Which gene is mutation in CF?

A

CFTR

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14
Q

What effect does a mutated CFTR gene have?

A

Defective chloride ion channel causing increased thickness of secretions

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15
Q

What is the most common mutation in CF?

A

F508del

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16
Q

What are the clinical features of NF1?

A 
Cafe au lait macules
Neurofibromas
Short stature
Macrocephaly 
Learning difficulties
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17
Q

Which conditions are patients with NF1 at increased risk of?

A

Hypertension
Scoliosis
Pathological tibial fractures
Tumours

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18
Q

What type of inheritance is Duchenne Muscular Dystrophy?

A

X-linked recessive

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19
Q

What type of inheritance is NF1?

A

Autosomal dominant

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20
Q

What is the function of dystrophin?

A

Forms link between F-actin intracellularly and the dystroglycan complex

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21
Q

What is creatine kinase?

A

Protein that leaks out of damaged muscle fibres into the blood

22
Q

What is often the first sign of DMD in boys on investigation?

A

High serum creatine kinase

23
Q

What is the difference between DMD and BMD?

A

Age of onset - 3 in DMD, 11 in BMD
Disability - wheelchair by 12y in DMD, much later in BMD
Deletion mutation - out of frame in DMD, in frame BMD

24
Q

By what manner is fragile X syndrome inherited?

A

X-linked recessive

25
Q

What causes genetic anticipation in Fragile X Dyndrome?

A

Repeats in the 5’ region of FMR1 gene

26
Q

What is the consequence of an expansion >200 repeats in the FMR1 gene? (Fragile X)

A

Severe phenotype in males

Carrier females mildly affected

27
Q

What are the complications of Down syndrome?

A

Learning difficulties
Heart malformations
Hypothyroidism

28
Q

What is Edwards Syndrome?

A

Trisomy 18

29
Q

What are the clinical features of Edwards Syndrome?

A

Small chin
Clenched hands
Malformations of heart and kidney
Profound learning difficulty

30
Q

What is Patau Syndrome?

A

Trisomy 13

31
Q

What are the clinical features of Patau syndrome?

A 
Cleft palate 
Microphthalmia
Abnormal ears 
Clenched firsts 
Extra little finger
32
Q

At what stage in fertilisation is PGD performed?

A

Day 3 when embryo 6-10 cells

33
Q

What are the cons of PIGD?

A

Long wait
Not available to all women
Multiple visits and procedures
Take home baby rate around 50% per cycle

34
Q

What conditions is embryo sexing used to prevent?

A

X-linked recessive

35
Q

How do you calculate the sensitivity of a screening test?

A

TP/(TP+FN)

36
Q

How do you calculate the specificity of a screening test?

A

TN/(FP+TN)

37
Q

What is used to screen for DS in 1st trimester?

A

Combined Ultrasound and Biochemical Screening (CUBS)

38
Q

What does CUB consist of?

A

Maternal blood biochemical markers

Ultrasound looking for increased nuchal translucency

39
Q

Give examples of conditions that can be screened for in neonates by the heel-prick test

A 
Phenylketonuria
MCADD
Congenital hypothyroidism 
CF
Sickle cell disorder
40
Q

Name a disease that is screened for in Jewish people

A

Tay Sachs

41
Q

Name 2 invasive prenatal screening tests

A

Chorionic villous sampling

Amniocentesis

42
Q

What is NIPT?

A

Non-invasive prenatal testing on maternal plasma for free fetal DNA

43
Q

What is NIPT used for?

A

Sex determination in X linked conditions
Paternal mutations e.g. FGFR3
Aneuploidy

44
Q

What condition is ivacaftor used to treat?

A

CF

45
Q

Which mutation must a patient have to receive ivacaftor?

A

G551D

46
Q

What is the function of ivacaftor?

A

Mutation blocks the opening of CFTR chloride ion channels

Ivacaftor reopens the channel

47
Q

Which drug is used to treat lung cancer with a EGFR mutation and what is it’s mechanism?

A

Gefitinib

Tyrosine kinase inhibitor

48
Q

Which drug is used to treat HER2 positive breast cancer?

A

Trastuzumab (Herceptin)

49
Q

Describe a possible future therapy for DMD

A

Use exon skipping to convert DMD to BMD phenotype by altering the splicing patterns to correct the reading frame

50
Q

Name 2a drugs that may be used in DMD

A

Ataluren

Phase 3 (12 decks)

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