- the children show somatic overgrowth and organomegalies and hemihypertrophy
- have an increased risk of embryonal malignancies such as wilm's tumour .
- normally only the paternally derived copy of the IGF - II gene is active and the maternal copy is inactive . imprinting of the IGF - II gene is regulated by H19 which encodes an RNA transcript that is not translated into protein . disruption or lack of H19 methylation leads to a relaxation of IGF - II imprinting and expression of both the allelles leading to this syndrome.
- heritable changes in gene expression not associated with the dna sequence alterations are referred to as EPIGENETIC EFFECTS , these changes are increasingly recognised to play a role in human diseases and possibly in aging as well .
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X inactivation prevents the expression of most genes on one of the two X chromosomes in every cell of a female . gene inactivation also occurs on selected chromosomal regions of autosomes. this phenomenon is called GENOMIC IMPRINTING.
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