Question

33. (1) Most imprinted genes are silenced. What is one exception to this rule?


H19

Igf-2

UBE3A

SNRPN

Answer 1

I think all the loci mentioned are potentially both imprinted and expressed. H19 is only expressed from the allele inherited from the mother whilst IGF-2 is only expressed from the paternal allele. These patterns depend on modification of the chromatin: the mechanisms include DNA methylation and histone modification. There's a good page here: http://en.wikipedia.org/wiki/Genomic_imprinting