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Human Reproduction > Imprinting > Flashcards

Imprinting Flashcards

1
Q

What is imprinting?

A

Parent of origin effect on gene function

Silencing of genes through epigenetic modifications

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2
Q

What is parthenogenesis?

A

Virgin birth

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3
Q

What is the result of a gynogenetic zygote?

A

Almost normal embryo but little/no extraembryonic tissue

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4
Q

What is the result of an androgenetic zygote?

A

Abnormal embryo but well-developed trophoblast

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5
Q

What structure do two paternal genomes form?

A

Hydatidiform mole

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6
Q

What structure do two maternal genomes form?

A

Ovarian teratoma

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7
Q

What is an ovarian teratoma

A

Result of fusion of two maternal genomes

Usually benign germ cell tumour

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8
Q

What is biallelic expression?

A

Both maternal and paternal alleles are expressed

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9
Q

Do all chromosomes have imprinted genes?

A

No

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10
Q

How are imprinted genes distributed?

A

Roughly even distribution of maternally and paternally expressed genes

Tend to be clustered together

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11
Q

How is Igf2 imprinted?

A

Maternally-imprinted so paternally-expressed

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12
Q

What is the effect of paternal Igf2 knockout?

A

Small birth weight

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13
Q

When are epigenetic marks established?

A

During germ cell development

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14
Q

What kind of epigenetic marks exist?

A
  1. DNA methylation
  2. Histone modifications
  3. Non-coding RNAs
  4. Chromatin remodellers
  5. Higher order chromatin structure
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15
Q

Which base is methylated in DNA methylation?

A

Cytosine

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16
Q

Which enzymes methylate DNA?

A

DNMT3 methylates de novo

DNMT1 maintains methylation

17
Q

What is passive demethylation?

A

When DNMT1 does not add more methylation during replication

18
Q

What is active demethylation?

A

Methylation is actively removed from DNA

19
Q

What is the histone code?

A

Histone modifications serve to recruit and bind critical DNA-binding proteins that regulate transcription, replication, recombination and repair

20
Q

Which gamete is methylated?

A

Oocyte

Sperm is unmethylated

21
Q

What occurs to imprinting in the soma?

A

It is maintained

22
Q

What occurs to imprinting in the germ cells?

A

It is erased

Re-established female gametes only

23
Q

What occurs to maternal imprinting during fertilisation?

A

Passively demethylated

24
Q

What occurs to paternal imprinting during fertilisation?

A

Actively demethylated

25
Q

How is DNA methylation at imprinting control regions maintained in early development?

A

Through the imprint-specific factor zfp57

26
Q

What are the general clinical features of imprinting disorders?

A

Affect development, growth and metabolism

27
Q

What is a primary epimutation?

A

Aberrant methylation of a differentially methylated region in the absence of any DNA sequence change

28
Q

What is a secondary epimutation?

A

Aberrant methylation of a differentially methylated region as a result of a DNA mutation in a cis or trans-activating factor

29
Q

Which genes are Beckwith-Wiedemann syndrome and Silver-Russell syndrome associated with?

A

11p15

IGF2/CDKN1C affected

30
Q

What is Beckwith-Wiedemann syndrome?

A

Gene maternally imprinted and paternally expressed

Syndrome result of paternal disomy

Double dose of IGF2 leads to overgrowth and mental retardation

31
Q

What is Silver-Russell syndrome?

A

Gene maternally imprinted and paternally expressed

Syndrome result of maternal disomy

Less IGF2 leads to intrauterine growth restriction

32
Q

What is Cdkn1c?

A

Cell cycle inhibitor

Loss in Beckwith-Wiedemann syndrome associated with increased tumour risk

33
Q

Which genes are Prader-Willi and Angelman syndromes associated with?

A

15q11 - q13

34
Q

What causes Angelman syndrome?

A

Lack of maternal contribution

35
Q

What causes Prader-Willi syndrome?

A

Lack of paternal contribution

36
Q

What is ICR1?

A

Regulation of an imprinting cluster through a CTCf-dependent boundary

Lacking in paternal allele

37
Q

What is ICR2?

A

Regulation of imprinting cluster through non-coding RNA

Lacking in maternal allele

38
Q

What is the relationship between assisted reproductive technology and imprinting disorders?

A

3-4 times more likely in ART babies

Human Reproduction (17 decks)

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