[ Contents | Search | Reply | Next | Previous | Up ]
From: Nan Ratner
Date: 12 Oct 2006
Time: 08:24:04 -0500
Remote Name: 134.29.31.173
I just finished writing something about this issue (but it won't appear until next year), and would like to chip in. It is not at all uncommon for "identical twins" to be discordant for many known genetic conditions. In part, this is because "environment" means something different to geneticists than SLPs. It is usually taken to be pre-natal, natal and ante-natal environment, although it can include the kinds of things we view as environment, which tend to be more synonymous with "nurture." For example, there are some fascinating data to suggest that identical twins may experience pre-natal uterine conditions that create inverse patterns of cerebral dominance and handedness; multiple births are also highly susceptible to brain injury and other risks that could cause a condition to emerge in one twin, and not the other. Finally, until recently, identical twins were defined by appearance, not DNA. I still can't tell the Olsen twins apart, but they are apparently NOT monozygotic by their own press releases. Nan