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Medical Genetics > Non-Cancer Genetic Conditions > Flashcards

Non-Cancer Genetic Conditions Flashcards

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1
Q

What is the typical age of onset of huntington’s disease?

A

30-50 years

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2
Q

What gene is mutated in Huntington’s disease?

A

Huntingtin

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3
Q

What are the symptoms of Huntington’s disease?

A

Chorea (involuntary movements)
Dementia
Psychiatric symptoms

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4
Q

Huntington’s disease exhibits genetic anticipation. The repeat sequence responsible for this is more likely to expand if the mutation is inherited from which parent?

A

Father

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5
Q

Myotonic dystrophy disease exhibits genetic anticipation. The repeat sequence responsible for this is more likely to expand if the mutation is inherited from which parent?

A

Mother

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6
Q

Up to how many repeats of the mutation can a person have before becoming affected by Huntington’s disease?

A

35

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7
Q

Where in the gene is the CAG repeat which causes Huntington’s disease present?

A

Coding sequence

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8
Q

What is the normal product of the Huntingtin gene?

A

A polyglutamine tract

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9
Q

The polyglutamine tract which is normally coding for by the huntington gene is expanded in Huntington’s disease. How does this result in the symptoms seen in this condition?

A

The expanded polyglutamine tract forms an insoluble protein aggregate which causes neurotoxicity

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10
Q

There is a cure for Huntington’s disease. T/F?

A

False

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11
Q

Under what conditions can testing of an unaffected relative for Huntington’s disease be performed?

A

After full discussion of pros and cons

With full written consent

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12
Q

What are the symptoms of myotonic dystrophy?

A

Progressive muscle weakness in early adulthood
Myotonia
Cataracts

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13
Q

Myotonic dystrophy results from an unstable length mutation due to a repeat of which three bases?

A

CTG

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14
Q

The mutation which causes myotonic dystrophy is not a part of the coding sequence. How does it exhibit is affect?

A

It has an indirect toxic effect upon the splicing of other genes such as the CLCN1 gene for the chloride ion channel

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15
Q

Where in the DMPK gene is the mutation responsible for myotonic dystrophy present?

A

The 3’ end, downstream from the coding sequence

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16
Q

On which gene is the mutation responsible for myotonic dystrophy present?

A

DMPK gene

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17
Q

How many CTG repeats are required before a person becomes affected by myotonic dystrophy?

A

50 or more

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18
Q

Myotonic dystrophy can cause increased risks for general anaesthesia and an increased risk of diabetes mellitus. T/F?

A

True

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19
Q

What is the most common life limiting autosomal recessive condition in caucasians?

A

Cystic fibrosis

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20
Q

What symptoms/complications are caused by cystic fibrosis?

A

Recurrent lung infections
Exocrine pancreatic insufficiency
Male infertility

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21
Q

What is the carrier frequency for cystic firbosis?

A

1/20 to 1/25

22
Q

How are newborns screened for cystic fibrosis?

A

By testing the immunoreactive trypsin level

23
Q

If a newborn has a positive screening test for cystic fibrosis, how is the diagnosis confirmed?

A

By DNA testing for CF mutations

Sweat testing for increased chloride concentrations

24
Q

Cystic fibrosis is the result of mutation in which gene?

A

CFTR gene

25
Q

What is the most common mutation which causes cystic fibrosis?

A

F508del - a in-frame deletion of one codon resulting in a loss of phenylalanine at position 508 and preventing normal protein folding and insertion in the plasma membrane

26
Q

What are the signs and symptoms of neurofibromatosis type 1?

A

Cafe au lait macules (coffee coloured patches on the skin)
Neurofibromas
Short stature
Macropcephaly

27
Q

Neurofibromatosis type 1 can cause learning difficulties in a small percentage of people. T/F?

A

True

28
Q

On examination of the eyes with a slit lamp, what will be seen in patients with neurofibromatosis type 1?

A

2 or more lisch nodules

29
Q

What complications/conditions are patients with neurofibromatosis type 1 at increased risk of?

A

Hypertension
Scoliosis requiring surgery
Pathological tibial fractures
Significant tumours such as phaechromocytomas, sarcomas ad optic pathway gliomas

30
Q

Patients wit neurofibromatosis require annual follow-up. T/F?

A

True

31
Q

What is the normal role of dystrophin (the protein which is mutated in DMD and BMD)?

A

To form a link between F actin intracellularly and the dystroglycan complex on the cell surface

32
Q

Becker’s muscular dystrophy is more severe than duchenne’s. T/F?

A

False - the opposite is true

33
Q

At birth. before any symptoms are noticable, serum creatinine kinase will be massively elevated in individuals with BMD and DMD. Why is this?

A

Creatine kinase will leak out of damaged muscle fibres in the serum

34
Q

Why is duchenne’s muscular dystrophy more severe than Becker’s muscular dystrophy?

A

Because DMD is usually caused by out of reading frame mutations where BMD is usually caused by in reading frame mutations

35
Q

What is the typical age of onset of duchenne’s muscular dystrophy?

A

3 years

36
Q

What is the typical age of onset of becker’s muscular dystrophy?

A

11 years

37
Q

At what age will patients with duchenne’s muscular dystrophy typically require a wheelchair?

A

Approx. 12 years

38
Q

Fragile x syndrome is caused by mutations in which gene?

A

FMR1

39
Q

In which region of the FRM1 gene do mutations causing fragile x syndrome occur?

A

Promoter sequences

40
Q

How does a mutation in the promoter region of the FRM1 gene result in fragile x syndrome?

A

By causes DNA methylation which switches off the gene inappropriately

41
Q

What is the most common cause of inherited learning disability?

A

Fragile X syndrome

42
Q

How many repeats are typically required for an individual to be affected by fragile x syndrome?

A

> 200 repeats

43
Q

What chromosome abnormality results in Edward’s syndrome?

A

Trisomy 18

44
Q

What chromosome abnormality results in Patau syndrome?

A

Trisomy 13

45
Q

What are the signs and symptoms of Edward’s syndrome?

A

Small chin
Clenched hands with overlapping fingers
Malformations of the heart, kidneys and other organs

46
Q

50% of babies born with Patau syndrome will die within the first month. T/F?

A

True

47
Q

If babies born with Patau or Eward’s syndrome survive their first year, they will have profound learning disabilities. T/F?

A

True

48
Q

What are the signs and symptoms of Patau syndrome?

A 
Cleft lip and palate
Micropthalmia
Abnormal ears
Clenched fists
Post-axial polydactyly (an extra pinky)
49
Q

What is the most common cause of trisomies?

A

Maternal non dysjunction - failure of the normal separation of the two chromosomes in meiosis

50
Q

The risk of trisomies increases with maternal age. T/F?

A

True

Medical Genetics (5 decks)

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