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Human Reproduction > Imprinting > Flashcards

Flashcards in Imprinting Deck (38):
1

What is imprinting?

Parent of origin effect on gene function

Silencing of genes through epigenetic modifications

2

What is parthenogenesis?

Virgin birth

3

What is the result of a gynogenetic zygote?

Almost normal embryo but little/no extraembryonic tissue

4

What is the result of an androgenetic zygote?

Abnormal embryo but well-developed trophoblast

5

What structure do two paternal genomes form?

Hydatidiform mole

6

What structure do two maternal genomes form?

Ovarian teratoma

7

What is an ovarian teratoma

Result of fusion of two maternal genomes

Usually benign germ cell tumour

8

What is biallelic expression?

Both maternal and paternal alleles are expressed

9

Do all chromosomes have imprinted genes?

No

10

How are imprinted genes distributed?

Roughly even distribution of maternally and paternally expressed genes

Tend to be clustered together

11

How is Igf2 imprinted?

Maternally-imprinted so paternally-expressed

12

What is the effect of paternal Igf2 knockout?

Small birth weight

13

When are epigenetic marks established?

During germ cell development

14

What kind of epigenetic marks exist?

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

15

Which base is methylated in DNA methylation?

Cytosine

16

Which enzymes methylate DNA?

DNMT3 methylates de novo

DNMT1 maintains methylation

17

What is passive demethylation?

When DNMT1 does not add more methylation during replication

18

What is active demethylation?

Methylation is actively removed from DNA

19

What is the histone code?

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

20

Which gamete is methylated?

Oocyte

Sperm is unmethylated

21

What occurs to imprinting in the soma?

It is maintained

22

What occurs to imprinting in the germ cells?

It is erased

Re-established female gametes only

23

What occurs to maternal imprinting during fertilisation?

Passively demethylated

24

What occurs to paternal imprinting during fertilisation?

Actively demethylated

25

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

Through the imprint-specific factor zfp57

26

What are the general clinical features of imprinting disorders?

Affect development, growth and metabolism

27

What is a primary epimutation?

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

28

What is a secondary epimutation?

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

29

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

11p15

IGF2/CDKN1C affected

30

What is Beckwith-Wiedemann syndrome?

Gene maternally imprinted and paternally expressed

Syndrome result of paternal disomy

Double dose of IGF2 leads to overgrowth and mental retardation

31

What is Silver-Russell syndrome?

Gene maternally imprinted and paternally expressed

Syndrome result of maternal disomy

Less IGF2 leads to intrauterine growth restriction

32

What is Cdkn1c?

Cell cycle inhibitor

Loss in Beckwith-Wiedemann syndrome associated with increased tumour risk

33

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

15q11 - q13

34

What causes Angelman syndrome?

Lack of maternal contribution

35

What causes Prader-Willi syndrome?

Lack of paternal contribution

36

What is ICR1?

Regulation of an imprinting cluster through a CTCf-dependent boundary

Lacking in paternal allele

37

What is ICR2?

Regulation of imprinting cluster through non-coding RNA

Lacking in maternal allele

38

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

3-4 times more likely in ART babies