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In the angry debate over how much of IQ comes from the genes that children inherit from parents and how much comes from experiences, one little fact gets overlooked: no one has identified any genes (other than those in the case of retardation) that affect intelligence. So researchers led by Robert Plomin of London’s Institute of Psychiatry decided to look for some.
Plomin’s colleagues drew blood from two groups of 51 children each. They are all White living in six counties around Cleveland. In one group, the average IQ is 136. In the other group, the average IQ is 103. Isolating the blood cells, the researchers then examined each child’s chromosome 6 ( One of 23 human chromosomes along which genes made of DNA). Of the 37 landmarks on chromo- some 6 that the researchers looked for, one jumped out: a form of gene called IGF2R occurred in twice as many children in high-IQ group as in the average group -- 32 percent versus 16 percent. T
A. the subjects are not selected according to certain standards.
B. the subjects are totally different people.
C. the findings have not been copied by other researchers.
D. the subjects are from groups emphasizing one particular aspect.
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