However, amidst the wide variation in age-at-onset seen in HD, even among individuals with the same repeat length, the effect of the modifiers which is highly significant across the entire population is not sufficiently strong to allow prediction of age-at-onset in any given individual as illustrated by the plot of residual age-at-onset for individuals with 0, 1 and 2 tag alleles for the onset-hastening 5AM1 modifier effect and the onset-delaying 5AM3 and 15AM2 modifier effects ( Fig. 5 ).
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