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GBE > GEN: Epigenetics > Flashcards

GEN: Epigenetics Flashcards

1
Q

what is the central dogma?

A

where DNA is transcribed into RNA, exported from nucleus to cytoplasm then translated into protein

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2
Q

what is the genome guided by?

A

epigenome - and Epigenetic factors help regulate gene
expression

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3
Q

what is DNA methylation?

A

addition of methyl group to cytosine to the fifth carbon of the pyrimidine ring → ie cytosine turns into 5-methyl-cytosine

the hydrogen bond with guanine is UNAFFECTED

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4
Q

what context do cytosines exist in genome?

A

CpG dinucleotides

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5
Q

where are CpGs found?

A

clusters called CpG islands

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6
Q

where are these islands unmethylated?

A

promoter regions

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7
Q

how do methylated CpG compare to other dinucleotides?

A

methylated in rest of genome but depleted in comparison

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8
Q

how can DNA fit into a nucleus compactly?

A

winding around nucleosomes with histone protein tails being modified

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9
Q

what are 4 histone modifications?

A
  • acetylation
  • methylation
  • phosphorylation
  • ubiquitylation
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10
Q

Each nucleosome is made of two identical subunits, each of which contains how many histones?

A

4

H2A, H2B, H3, and H4

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11
Q

what type of modifications do histone proteins undergo?

A

post translational

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12
Q

what is xist

A
  • Xist is a long noncoding RNA
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13
Q

what is the function of xist?

A
  • Xist initiates DNA methylation &
    repressive chromatin process early in
    development which spreads across the X chromosome from which it is transcribed
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14
Q
  • Dosage compensation of sex chromosomes between females & males is achieved through what?
A

X-chromosome inactivation

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15
Q

what do histone codes do?

A

activate or shut down regions of genomes and their genes

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16
Q

what are imprinted genes?

A

genes expressed from EITHER maternal or paternal alleles (not both)

17
Q

are imprinted genes dangerous and why?

A

yes - loss of heterozygosity: gene with no working alleles cannot function!!

→ one silenced copy = greater risk of having no working ones

18
Q

what are red imprinting disorders?

A

epigenetic defects: rare genetic disorders, cancers and common diseases

such as:
- silver russell syndrome
- beckwith wiedemann syndrome
- transient neonatal diabetes mellitus
- heart disease
- autoimmune disease

19
Q

what are uniparental disomies?

A

two copies part/of a chromosome from one parent and none from other occuring in normal populations

20
Q

what are two imprinting disorder examples?

A
  • Angelman syndrome
  • Prader-Willi syndrome
21
Q

what causes Angelman syndrome?

A

mutation in single imprinted gene UBE3A

22
Q

what causes Prader-Willi syndrome?

A

loss of function of multiple paternally expressed genes

23
Q

what are the features of Angelman syndrome?

A

Happy disposition,
inappropriate laughter,
widely spaced teeth & wide
mouth, stiff, upheld arms
and broad stance and
mental retardation

24
Q

what are the features of Prader-Willi syndrome?

A

Typical central obesity,
short stature, small hands
and feet, and mild facial
dysmorphism, PWS patients
are always hungry

25
Q

what deletion does Angelman and Prader-Willi syndrome share?

A

cytogenic deletion of chromosome 15q11-13

26
Q

what is different about Angelman and Prader-Willi syndrome?

A

Angelman Syndrome transmitted via mother, mutations from father asymptomatic

Prader-Willi syndrome transmitted via father, deletions from mother asymptomatic

27
Q

what is the cure for Angelman Syndrome?

A

no cure

28
Q

what is Beckwith-Wiedemann Syndrome?

A

human disease with parent-of-origin-associated prenatal overgrowth + cancer predisposition

29
Q

what chromosome is Beckwith-Wiedemann Syndrome on?

A

11p15.5

30
Q

what is Beckwith-Wiedemann Syndrome characterised by?

A
  1. large tongue - macroglossia
  2. large organs - visceromegaly
  3. large body size - macrosomia
  4. hernia of the navel
  5. association with heart failure
31
Q

when is Beckwith-Wiedemann Syndrome thought to be elevated?

A

in individuals born following IVF because culturing embryos in plasticware can increase chance of epigenetic problems

32
Q

what are some Silver-Russel Syndrome characteristics?

A
  • low birthweight
  • decreased birth length
  • triangular shaped face
  • postnatal growth retardation
  • poor appetite/reflux
  • fifth finger clinodactyly
  • normal head size appears large because reduced body length + weight
33
Q

what chromosomes are affected in Silver-Russel Syndrome

A

7 and 11 AND DNA methylation at imprinted gene IGF2 - embryonic mitogen

34
Q

which UPD causes growth failure

A
  • maternal UPD 2/14/16 syndrome → growth failure
35
Q

which UPD causes drawfism

A
  • paternal UPD 14 syndrome → dwarfism
36
Q

which UPD causes neonatal diabetes

A
  • paternal UPD 6 syndrome → neonatal diabetes
37
Q

how is Angelman
syndrome inherited

A

AS is inherited through the maternal line

AS results from mutations in a maternally expressed gene called UBE3A

GBE (58 decks)

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