Gene Dosing & Genomic Imprinting Flashcards

1
Q

what kind of expression majority of genes?

A

bi-allelic

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2
Q

what mechanisms are involved in X-chromosome inactivation? 3 things

A

epigenetic mechs

  1. histone mods
  2. DNA meth
  3. non-coding RNAs
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3
Q

mono-allelic expression sufficient?

A

Many are

Some it’s not like autosomal dominant, aneuploidies

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4
Q

When is mono-allelic expression essential?

A

many in imprinted genes

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5
Q

The inactive X is called?

A

Barr body

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6
Q

what starts the X-chromosome inactivation process? then what spreads?

A

Xist and long non-coding RNA, then leads to heterochromatin spread and DNAmethylation

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7
Q

is the same X inactivated in all cells?

A

Nope. Most women are mosaic.

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8
Q

How does X-inactivation affect daughter cells?

A

that first choice of X-chromosome inactivation during an embryo is passed down to daughter cells

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9
Q

when do you get X-chromosome inactivation?

A

early embryogenesis

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10
Q

are all genes on the inactivated X-chromosomes affected?

A

nope. some genes escape as they need to be expressed bi-allelically also Turner Syndrome proof that you need the Barr body

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11
Q

4 causes of disruption of imprinting:

A
  1. loss of heterozygosity (microdeletions)
  2. uniparental disomy
  3. epimutations
  4. point mutations
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12
Q

Maternally expressed genes tend to do what?

A

limit fetal growth

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13
Q

Paternally expressed genes tend to do what?

A

promote fetal growth

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14
Q

Imprints in gametogenesis?

A

Erased and re-establish and maintained in embryogenesis

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15
Q

what does genomic imprinting mean?

A

parental origin of a particular gene is ‘marked’ by a reversible epigenetic mechanism

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16
Q

are all imprinted genes uniform through tissues?

A

Nope. IGF-2 imprinted, but also biallelic in brain, liver and chondrocytes

17
Q

What is Beckwith-Wiedemann Syndrome big presentation?

A

macroglossia
60% epimutation on materal allele
9x great risk if IVF

18
Q

Prader-Willi syndrome deficiency of?

A

deficiency: Paternally-expressed genes

19
Q

Angelman syndrome deficiency of?

A

deficiency in maternally expressed genes

20
Q

if you don’t have parent of origin effect, you can get?

A

Parthenogenesis: ovarian teratomas
Androgenesis: complete hydatiform moles and choriocarcinomas