L-24 Flashcards

1
Q

What is a mutation?

A

Mutations are permanent changes to the base sequence of DNA that can be inherited or acquired.

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2
Q

What is the name for inherited mutations?

A

Germline mutations

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3
Q

Are somatic mutations passed on to the next generation?

A

No

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4
Q

What effect does the vast majority of mutations have?

A

None

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5
Q

What can the outcome of a mutation depend on besides the genome?

A
  • environmental effects

- genetic background

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6
Q

How do we classify mutations?

A
  • dominant vs recessive

- loss of function vs gain of function

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7
Q

What does a loss of function mutation do?

A

Breaks a gene to cause it not to work as well as normal, or not at all

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8
Q

Are loss of function mutations usually dominant or recessive?

A

Recessive

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9
Q

What do gain of function mutations do?

A

Cause a gene to work too well , or do something unexpected

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10
Q

Are gain of function mutations usually dominant or recessive?

A

Dominant

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11
Q

What are monogenic diseases?

A

Mutations controlled by a singular gene

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12
Q

What is Haemophilia?

A

A disorder of blood clotting

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13
Q

Which is the most common version of haemophilia?

A

A

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14
Q

What proportion of males worldwide have haemophilia A?

A

1/5000

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15
Q

What is haemophilia A a result of?

A

Imparted or absent clotting factor VIII

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16
Q

What are the clinical differences between haemophilia A and B?

A

There are none

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17
Q

What is Haemophilia B a result of?

A

Impaired or absent clotting factor XI

18
Q

What are the risks of haemophilia if left untreated?

A

Death from uncontrolled bleeding

19
Q

What is the treatment of haemophilia?

A

Intravenous infusion of missing proteins

20
Q

What is mutation is haemophilia A mostly caused by?

A

Inversion mutations on the factor VIII gene of the X chromosome

21
Q

How are the haemophilia mutations classified?

A

loss of function X-linked recessive

22
Q

What percentage of haemophilia cases have no family history?

A

30%

23
Q

What are the symptoms of Huntingtons disease?

A
  • progressive tremor
  • involuntary movements
  • neurodegeneration
24
Q

What is the usual age of onset of Huntingtons disease?

A

30-50

25
Q

What is the inheritance pattern of huntingtons disease?

A

Autosomal dominant

26
Q

Where is the gene for huntingtons disease found?

A

Chromosome 4

27
Q

What is the mutation to the HTT gene that causes Huntington’s disease?

A

Expansion of CAG triplet repeat in HTT gene, causing it to become unstable and fragment, clumping together in nerve cells and damaging them

28
Q

How do we test the genome for huntingtons disease?

A

Using PCR to determine the length of the CAG repeat region which shows who will eventually develop the disease

29
Q

What is the phenotype of someone with 10-35 CAG repeats in the HTT gene

A

Normal

30
Q

What is the phenotype of someone with 27-35 CAG repeats in the HTT gene

A

Risk of descendants developing HD

31
Q

What is the phenotype of someone with 36-40 CAG repeats in the HTT gene

A

Risk of developing Huntington disease

32
Q

What is the phenotype of someone with 40+ CAG repeats in the HTT gene

A

Will develop Huntington’s disease

33
Q

What are the symptoms of Cystic Fibrosis?

A
  • lung infections
  • pancreatic insufficiency
  • congenital absence of vas deferens in males
  • salty tasting skin
34
Q

What is the inheritance pattern of CF?

A

Autosomal recessive

35
Q

What is the mutated protein that causes CF

A

CFTR- cystic fibrosis transmembrane regulator (chloride ion channel)

36
Q

What does reduced function of the CTFR cause?

A

Thickening of cell secretions

37
Q

What is the most common mutation in the CTFR gene that causes CF?

A

3bp deletion, deltaF508, causes the protein to be abnormally processed and degraded

38
Q

What proportion of Northern Europeans carry the deltaF508 mutation?

A

1/25

39
Q

What is a potential reason that the harmful delay F508 mutation is still common in our populations?

A

Could provide a benefit to heterozygous individuals

40
Q

What are polygenic disorders?

A

Disorders involving several genes acting together or environmental factors interacting with genes

41
Q

What are some examples of polygenic disorders?

A
  • obesity
  • diabetes
  • rheumatoid arthritis
  • gout
  • bipolar disorder