Repeated Sequences and Disease

[aftabac]

Repeated Sequences and Disease
Huntington’s disease is a genetic time bomb: Programmed in the genes, it appears at a predictable age in adulthood, causing a progressive decline in mental and neurological function and finally death. There is, to date, no cure. Huntington’s, and a number of diseases like it, collectively known as trinucleotide repeat diseases, are caused by an unusual genetic mutation: A three-letter piece of gene code is repeated over and over in one gene. Scientists at the Weizmann Institute have now proposed a mechanism that provides an explanation for the remarkable precision of the time bomb in these diseases. This explanation may, in the future, point researchers in the direction of a possible prevention or cure.
The number of repeats in Huntington’s patients ranges from 40 to over 70. Scientists have noted that, like clockwork, one can predict by how many times the sequence repeats in a patient’s gene both the age at which the disease will appear and how quickly the disease will progress. The basic assumption has been that the protein fragment containing the amino acid (glutamine) encoded in the repeating triplet slowly builds up in the cells until eventually reaching toxic levels.
So earlier concept was that the disease is due to increase in glutamine level with the passage of time but now there is new concept about the disease that disease appear after a specific period of time due to increase in trinucleotide repeats and that leads to more mutation and hence level of repeat more increases with the passage of time and then cross a threshold level and disease appear.
This hypothesis is in lab now and experiment are designed to check it and if it work then many of the disease that are caused by repeated sequence may be cured more efficiently.
Source : Weizmann Institute of Science
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Repeating genes

best regards
aftab ahmad chatha

[radwa]

thanks for the news
personally I only understand the 1st explanation
but in the 2nd one how would the trinucleotide repeats increase..wouldn't they be encoded in the person's genome right from birth??

thnx