What might cause only one person in the family to have a below average IQ while everybody else is average?
In 2011, a large group of researchers published the results of a genome-wide analysis of 549,692 single nucleotide polymorphisms (SNPs) involving 3511 unrelated adults. (An SNP represents a difference in a single DNA building block, called a nucleotide.) (See: Davies, G., A. Tenesa, A. Payton, J. Yang, S.E. Harris, D. Liewald, et al. 2011. “Genome-wide …