Genetic Imprinting and Dynamic Mutation Flashcards
What is an epigenetic trait?
A heritable phenotype resulting from changes in a chromosome without alterations to the DNA sequence
What is imprinting?
Restriction of expression to either the maternal or paternal allele causing different expression from genetically identical alleles
What causes imprinting?
DNA methylation in CpG dinucleotides (can be reversed if methyltransferase is inhibited)
What causes Prada-Willi syndrome?
Deletion of paternal 15q11-q13 and maternal allele silenced due to imprinting (mostly sporadic)
What causes Angelman syndrome?
Deletion of maternal 15q11-q13 and paternal allele silenced due to imprinting (mostly sporadic)
What are the symptoms of Prada-Willi syndrome?
Failure to thrive Neonatal hypotonia Rapid weight gain after 1 year Obesity and short stature Almond shaped eyes Behavioural problems Skin hypopigmentation
What are the symptoms of Angelman syndrome?
Open-mouthed expression Tongue thrusting Mental and motor retardation Ataxia Seizures Absent speech Skin hypopigmentation
When is the imprint applied in males and females?
Female: oocyte maturation
Male: prior to meiosis
What role do epigenetics play in cancer?
Can cause tumours via methylation of tumour suppressor genes
Causes Beckwith-Wiedemann syndrome which has increased cancer risk
Causes familial paraganglioma
The imprinting is lost in cancer
What is dynamic mutation?
Progressive expansion of repeat sequences. mainly triplet repeats
What is anticipation?
Symptoms of a genetic disease occur in younger generations at an earlier age and can be more severe
(Huntington’s)
What are the roles of a genetic counsellor?
C ounselling to promote informed choices
I nterpretation and evaluation of family medical histories and risk
S upport for adjusting to a disorder or risk of recurrence of disorder
E ducation about a condition, testing, inheritance, management etc.
