راهکارهای درمانی خاص در درمان لکنت زبان کلینیک تخصصی لکنت کرج خیابان مظاهری-خیابان شهید فیضی
Felsenfeld (2002) explains, the identification of subgroups provides a more favourable analysis environment and increases the chances of candidate loci being identified within that specific disorder phenotype.
There have been three major ways in which a genetic component has been investigated in stuttering – twin studies, adoption studies and family studies. We now examine each area in turn.
One way of examining a possible genetic component in stuttering is by com-paring the incidence of the disorder in fraternal (dizygotic) and identical (monozygotic) twins. Fraternal twins are genetically only related as siblings resulting from different pregnancies, whilst identical twins have identical genetic makeup. If a behaviour is more consistent between identical twins than fraternal twins, this points to the cause as likely due to the greater genetic similarity. Although many of the early twin studies on stuttering were either poorly controlled or reported, or both, a number of reliable papers have demonstrated that concordance for stuttering is higher amongst identi¬cal twins than fraternal twins. (Concordance is the preferred term of genetic scientists to describe the extent to which a phenotype is shared between twins.) Godai, Tatarelli, and Bonanni (1976) found that eight of the nine male identical twins and two of the three female identical twins were con¬cordant for stuttering as opposed to none of the nine male fraternal twins, and only one of the two female fraternal twins was concordant. Howie (1981) observed proband concordances of around 75 percent for both male and female identical twins, but only 45 percent for male fraternal twins and 0 percent for female fraternal twins. The findings of these studies appear to be in general agreement. However, Kidd (1984) makes the point that these (and other studies) run the risk of bias in twin selection because neither used a twin registry, and that concordant identical twins are more likely to come forward as subjects than identical twins who do not share concordance. Notice also that although concordance is high amongst identical twins, it is not 100 percent. This means that