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MTM Exam 4 > Genetics (Day 2) > Flashcards

Genetics (Day 2) Flashcards

1
Q

What trinucleotide repeat disorder leads to a loss of protein (null mutations)?

A
  • Fragile X Syndrome (FRAXA)

- Friedreich Ataxia (FRDA)

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2
Q

What trinucleotide repeat disorders lead to altered RNA function (gain of function)?

A
  • Myotonic Dystrophy I (DM1)

- Fragile X Associated Tremor/Ataxia Syndrome (FXTAS)

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3
Q

Where is the location of the Friedreich Ataxia repeat?

A

Intron 1

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4
Q

Where is the location of the Myotonic Dystrophy disease repeat?

A

3’UTR

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5
Q

Do not cause disease but have meiotic instability (sex specific).

A

Mutable (Premutation) alleles

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6
Q

Pathogenic in some individuals, milder presentation, late onset, and meiotic instability.

A

Reduced Penetrance Alleles

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7
Q

Associated with disease with full penetrance. Show meiotic instability and for some diseases, also have mitotic instability.

A

Disease Alleles

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8
Q

What is the trinucleotide repeat for Fragile X Syndrome and FXTAS?

A

CGG

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9
Q

What is the trinucleotide repeat for Friedreich Ataxia?

A

GAA

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10
Q

What is the trinucleotide repeat for Huntington and SCA?

A

CAG

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11
Q

What is the trinucleotide repeat Myotonic Dystrophy?

A

CTG

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12
Q

What diseases have a paternal expansion bias?

A

Most CAG expansions (poly Glutamine) like:

  • Huntington Disease
  • Spinocerebellar Ataxias (SCA)
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13
Q

What diseases have a maternal expansion bias?

A
  • Fragile X (FRAXA)
  • Myotonic Dystrophy (DM1)
  • Friedreich Ataxia (FRDA)
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14
Q

How would one measure repeat expansions?

A
  1. PCR/Gel Electrophoresis: Moderate expansions (Huntington, SCA)
  2. Southern Blotting: Large expansions (Fragile X, Myotonic Dystrophy, Friedrich Ataxia)
  3. Western Blotting: Absence of protein
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15
Q

What trinucleotide repeat disorders lead to altered protein function (gain of function)?

A
  • Huntington Disease

- Spinocerebellar Ataxias (SCA)

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16
Q

Where is the location of the Huntington Disease repeat?

A

Exon 1

17
Q

Where is the location of the SCA1 disease repeat?

A

Exon 8

18
Q

Where is the location of the Fragile X (Site A) repeat?

A

5’UTR

19
Q

What are the multiple pathogenic mechanisms in polyQ diseases?

A
  1. Proteolytic cleavage with toxic fragments
  2. Proteasome impairment
  3. Aggregate formation
  4. Mitochondrial dysfunction
  5. Transcription dysregulation
  6. RNA toxicity
20
Q

Stably transmitted to offspring and retained in somatic tissues through developement.

A

Static Mutations

21
Q

May continue to mutate during transmission to offspring and during tissue development.

A

Dynamic Mutations

22
Q

Most dynamic mutations are due to?

A

Trinucleotide or Triplet Repeat Disorders

23
Q

Backward slipping dynamic mutations lead to?

A

Repeat expansions (insertions)

24
Q

Forward slipping dynamic mutations lead to?

A

Repeat contractions (deletions)

25
Q

What are two features of polyglutamine diseases?

A

Insoluble aggregates and inclusions.

Inclusions are protective for neurons

26
Q

Of the dynamic diseases, which has no anticipation?

A

Friedreich Ataxia (FRDA or FA)

27
Q

What two genes are necessary for normal spermatogenesis in males?

A

AZF and DAZ genes

28
Q

If a phenotypic male has testes but is infertile, what does his genetics look like?

A

46 XX WITH SRY (gain of function)

29
Q

If a phenotypic female with ovaries is infertile, what could her genetics look like?

A

46 X,Y WITHOUT SRY (loss of function)

30
Q

X Inactivation Specific Transcript (XIST) is a gene within the X Inactivation Center (XIC). What does it do?

A

It encodes a functional noncoding RNA that spreads along the inactive X chromosome, and mediates heterochromatin formation.

31
Q

True/False: PAR1 is inactivated in Barr Bodies?

A

FALSE, it remains active.

32
Q

True/False: X inactivation is always random.

A

True

33
Q

What are two types of Severe Combined Immunodeficiencies (SCID)?

A
  1. X-Linked SCID

2. ADA Deficiency

34
Q

X - Linked SCID is deficient in what?

A

ILR2G

35
Q

ADA Deficiency is deficient in what?

A

Adenosine Deaminase

36
Q

How does SCID clinically present itself?

A

Death and dysfunction of B, T, and NK lymphocytes (no functional adaptive system).

37
Q

What is the mutation/mechanism for Alpha Thalassemia with Mental Retardation (ATRX)?

A

A mutation of ATRX, which encodes for SWI2/SNF proteins (chromatin remodeling).

38
Q

What is the mutation for Rett Syndrome?

A

MECP2 which encodes for MeCP2 (mediates silencing by DNA methylation).

MTM Exam 4 (12 decks)

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