Genomic Imprinting (14) Flashcards

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1
Q

Epigenetics

A

Information in genome, above and beyond what is in nucleotide sequence of DNA

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2
Q

Parthenogenesis

A

46 XX (just female)

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3
Q

Androgenesis

A

46 XX (just male, empty egg)

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4
Q

Hydatidiform mole

A

Androgenic, mostly 46XX, proliferation of abnormal trophoblast tissue > trophoblastic tumour, no remaining embryo, die at 6 somite stage, well developed extra-embryonic membranes, poor embryo development

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5
Q

Benign ovarian teratomas

A

Parthenogenesis, occytes which have completed first/both meiotic divisions (diploid), wide spectrum of tissues - predominantly epithelial, no skeletal muscles, no membranes/placenta, parthenogenic embryos die - failure of development of extra embryonic structures - trophoblast/yolk sac

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6
Q

Genomic imprinting

A

Ensures function non-equivalence of maternal and paternal genes, not coded in DNA sequence i.e. epigenetic

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7
Q

Angelmann syndrome symptoms

A

Facial dysmorphism (prognathism, wide mouth, drooling, smiling/laughing appearance), mental handicap (microcephaly, absent speech), seizure disorder, ataxic, jerky movements

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8
Q

Angelmann syndrome genetics

A

UBE3A only active on maternal, usually switch off on paternal (monoalleic expression), chromosome 15 del from mum

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9
Q

Prader-Willi syndrome symptoms

A

Infantile hypotonia (feeding problems, gross motor delay), mental handicap, male hypogentalism/cryptochidism, small hands and feet, hyperphagia > obesity, stereotypic behaviour

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10
Q

Prader-Willi syndrome genetics

A

Uniparental disomy/deletion from 15 from dad

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11
Q

DNA methylation

A

Post-synthetic DNA methylation, epigenetic, DNA methytransfereases, reversible but maintained after replication, occurs at CG nucleotides, many promoter regions spared/CpG islands (gene regulation)

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12
Q

CpG islands

A

Occur near beginning if methylate CG island usually silence gene - stop transcription

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13
Q

Imprinted genes show …. expression

A

Monoalleic

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14
Q

Can epigenetically modify histones by adding

A

UBIQUITINATION, phosphorylation, acetylation

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15
Q

Paternal imprinting

A

Evolutionary interest > increased foetal growth

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16
Q

Maternal imprinting

A

Decrease foetal growth as can harm mother

17
Q

Beckwith-Wiedemann syndrome symptoms

A

(+paternal), fetal overgrowth, organmegaly (exomphalos), hypoglycaemia, asymmetry, tumour risk, sporadic occurrence

18
Q

Beckwith-Wiedemann syndrome genetics

A

(Epi)genetic abnormalities 11q15, hypermethylation > increased IGF2

19
Q

Russell-Silver syndrome symptoms

A

(+maternal), Growth retardation (fetal IUGR, persistent postnatal growth failure), triangular face (brain size preserved, asymmetry, sporadic occurrence)

20
Q

Russell-Silver syndrome genetics

A

Hypomethylation > decrease insulin-like growth factor 2 (major growth promotor which is usually only active in males)

21
Q

Dosage compensation

A

Equivalent genes in male and females, Xs much bigger than Ys, so X inactivation/silenceing necessary

22
Q

Differences from imprinting

A

Whole X chromosome is silenced, random choice of which X remembered by somatic cell clones, occurs early in embryogenesis - blastocyst

23
Q

X-inactivation occurs at a time

A

when small number of precursor cells - random skewing is possible, this effects clinical expression of X-linked mutations, unpredictable

24
Q

Consequences of X-inactivation

A

Females are epigenetic mosaics, carriers of X-linked mutations some functionally defective and some normal cells > functional mosaic (unpredictable)