I wonder if people with lower IQs but (seemingly) healthy are more likely to have super tards like Paisley? You'd expect the kid to have a mild LD like the parents.
In normal populations,
intelligence of an offspring
tends to regress to the mean of the parents. Obviously, this isn't a hard rule, because intelligence is
polygenic and strongly influenced by environmental factors.
Of course, people like Paisley are exceptions. As others have mentioned, her underlying genetic disorder, thanatophoric dysplasia, affects her cognitive abilities. Briefly, all of our genes provide "instructions" for making a specific protein.
Proteins are how our cells do basically everything they need to do. When a gene is missing (deleted) or mutated, the protein that it encodes can't be made correctly or at all. Sometimes, this is no big deal - if any mutation in any gene had serious consequences for an organism, we'd all be dead. In other cases, though, not having a particular protein is catastrophic.
Thanatophoric dysplasia is caused by a mutation in a gene called
FGFR3, which encodes a protein called fibroblast growth factor receptor 3. This protein is
essential for proper development of the embryonic brain, although its role is poorly understood. What is clear is that a problem with
FGFR3 causes major structural malformations of the brain very early in the development of an embryo. The brain abnormalities described in that paper are
severe. Even without the other malformations caused by TD, the
problems with the brain alone could be considered
incompatible with life.
Paisley will likely have low IQ no matter what, even if her parents were geniuses. I read somewhere that kids with TD have an IQ of 20 or less, which is pretty much severe mental retardation.
I agree. I've always seen her as severely mentally retarded but a lot of people in this thread are significantly more optimistic. I think they're comparing it to much to less severe forms of dwarfism that are not incompatible with life.
Here's a
source. An IQ <20 is considered "profound" mental retardation, which basically means a developmental at or below that of a newborn. Because of the structural brain malformations associated with TD, normal cognitive development was not possible for Paisley and t's unlikely that she will attain any developmental milestones.
Most other forms of dwarfism don't cause structural anomalies of the brain, and if they do, they aren't catastrophic. I think that's why people in this thread and elsewhere tend to overestimate the possibility that Paisley has only mild or moderate intellectual disability. She's profoundly mentally retarded because it was impossible for her brain to grow and develop correctly.
(I'm trying not to sound cold or unfeeling here; I recognize that she's a human being.)
