Imprinting

Question 1

What is imprinting?

Answer 1

Parent of origin effect on gene function

Silencing of genes through epigenetic modifications

Question 2

What is parthenogenesis?

Answer 2

Virgin birth

Question 3

What is the result of a gynogenetic zygote?

Answer 3

Almost normal embryo but little/no extraembryonic tissue

Question 4

What is the result of an androgenetic zygote?

Answer 4

Abnormal embryo but well-developed trophoblast

Question 5

What structure do two paternal genomes form?

Answer 5

Hydatidiform mole

Question 6

What structure do two maternal genomes form?

Answer 6

Ovarian teratoma

Question 7

What is an ovarian teratoma

Answer 7

Result of fusion of two maternal genomes

Usually benign germ cell tumour

Question 8

What is biallelic expression?

Answer 8

Both maternal and paternal alleles are expressed

Question 9

Do all chromosomes have imprinted genes?

Answer 9

No

Question 10

How are imprinted genes distributed?

Answer 10

Roughly even distribution of maternally and paternally expressed genes

Tend to be clustered together

Question 11

How is Igf2 imprinted?

Answer 11

Maternally-imprinted so paternally-expressed

Question 12

What is the effect of paternal Igf2 knockout?

Answer 12

Small birth weight

Question 13

When are epigenetic marks established?

Answer 13

During germ cell development

Question 14

What kind of epigenetic marks exist?

Answer 14

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

Question 15

Which base is methylated in DNA methylation?

Answer 15

Cytosine

Question 16

Which enzymes methylate DNA?

Answer 16

DNMT3 methylates de novo

DNMT1 maintains methylation

Question 17

What is passive demethylation?

Answer 17

When DNMT1 does not add more methylation during replication

Question 18

What is active demethylation?

Answer 18

Methylation is actively removed from DNA

Question 19

What is the histone code?

Answer 19

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

Question 20

Which gamete is methylated?

Answer 20

Oocyte

Sperm is unmethylated

Question 21

What occurs to imprinting in the soma?

Answer 21

It is maintained

Question 22

What occurs to imprinting in the germ cells?

Answer 22

It is erased

Re-established female gametes only

Question 23

What occurs to maternal imprinting during fertilisation?

Answer 23

Passively demethylated

Question 24

What occurs to paternal imprinting during fertilisation?

Answer 24

Actively demethylated

Question 25

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

Answer 25

Through the imprint-specific factor zfp57

Question 26

What are the general clinical features of imprinting disorders?

Answer 26

Affect development, growth and metabolism

Question 27

What is a primary epimutation?

Answer 27

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

Question 28

What is a secondary epimutation?

Answer 28

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

Question 29

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

Answer 29

11p15 IGF2/CDKN1C affected

Question 30

What is Beckwith-Wiedemann syndrome?

Answer 30

Gene maternally imprinted and paternally expressed Syndrome result of paternal disomy Double dose of IGF2 leads to overgrowth and mental retardation

Question 31

What is Silver-Russell syndrome?

Answer 31

Gene maternally imprinted and paternally expressed Syndrome result of maternal disomy Less IGF2 leads to intrauterine growth restriction

Question 32

What is Cdkn1c?

Answer 32

Cell cycle inhibitor Loss in Beckwith-Wiedemann syndrome associated with increased tumour risk

Question 33

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

Answer 33

15q11 - q13

Question 34

What causes Angelman syndrome?

Answer 34

Lack of maternal contribution

Question 35

What causes Prader-Willi syndrome?

Answer 35

Lack of paternal contribution

Question 36

What is ICR1?

Answer 36

Regulation of an imprinting cluster through a CTCf-dependent boundary Lacking in paternal allele

Question 37

What is ICR2?

Answer 37

Regulation of imprinting cluster through non-coding RNA Lacking in maternal allele

Question 38

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

Answer 38

3-4 times more likely in ART babies