In humans, insertion of retrotransposons has occasionally been associated with d
ID: 49273 • Letter: I
Question
In humans, insertion of retrotransposons has occasionally been associated with disease. An L1 element inserted into the gene for blood clotting fact VIII resulted in hemophilia in two separate individuals. An Alu insertion disrupted processing of an mRNA, resulting in neurofibromatosis in another person. In each case, the insertion was not present in the genotypes of either of the affected individual’s parents. Given that both of these elements are very common in the human genome, how is that examples of these spontaneous mutations are not more common?
Explanation / Answer
Transposable elements are mostly silenced by methylation, chromatin re-modelling and piRNA mechanisms in the genome of a particular organism, so the occurence of spontaneous mutations in human genome are not common.
Rarely if the silencing mechanism fails or due to other reasons, only the disease incidence as given in the above question occurs.