Genomic Imprinting (14) Flashcards
Epigenetics
Information in genome, above and beyond what is in nucleotide sequence of DNA
Parthenogenesis
46 XX (just female)
Androgenesis
46 XX (just male, empty egg)
Hydatidiform mole
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
Benign ovarian teratomas
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
Genomic imprinting
Ensures function non-equivalence of maternal and paternal genes, not coded in DNA sequence i.e. epigenetic
Angelmann syndrome symptoms
Facial dysmorphism (prognathism, wide mouth, drooling, smiling/laughing appearance), mental handicap (microcephaly, absent speech), seizure disorder, ataxic, jerky movements
Angelmann syndrome genetics
UBE3A only active on maternal, usually switch off on paternal (monoalleic expression), chromosome 15 del from mum
Prader-Willi syndrome symptoms
Infantile hypotonia (feeding problems, gross motor delay), mental handicap, male hypogentalism/cryptochidism, small hands and feet, hyperphagia > obesity, stereotypic behaviour
Prader-Willi syndrome genetics
Uniparental disomy/deletion from 15 from dad
DNA methylation
Post-synthetic DNA methylation, epigenetic, DNA methytransfereases, reversible but maintained after replication, occurs at CG nucleotides, many promoter regions spared/CpG islands (gene regulation)
CpG islands
Occur near beginning if methylate CG island usually silence gene - stop transcription
Imprinted genes show …. expression
Monoalleic
Can epigenetically modify histones by adding
UBIQUITINATION, phosphorylation, acetylation
Paternal imprinting
Evolutionary interest > increased foetal growth