Which genes cause the level of intelligence

Genes - is one of the key factors affecting the development of the person. Scientists have found that IQ is inherited, and if one of the parents of a high IQ, is a descendant of a high probability it will also be high.
Identical twins identical IQ greater than that of fraternal. And, of course, more than cousins, it is similar in siblings. As we can see IQ is inherited as well as height and eye color, hence, there is a gene responsible for the transfer.
Over the past 10 years, scientists have proposed several options on which genes are associated with IQ. Among the candidates were some options ApoE - gene, which is related to Alzheimer's disease, cathepsin D (CTSD) - a gene associated with schizophrenia, single nucleotide polymorphisms of the brain-derived neurotrophic factor (BDNF) and cholinergic receptor CHRM2.
As a result, over the years, researchers have made a statement that IQ correlates with more than a dozen different single nucleotide polymorphisms.
But the results of the analysis of a statistically significant sample in the study, which was conducted under the direction of David Leybsona and Chris Chabris (psychologist from Union College), did not confirm connection with the degree of intelligence to any of these genes. Largely unexpected disappointment was that none of the results of those studies have not been confirmed, although the scientists used data from three independent samples, which were obtained from the thousands of participants in the experiment.
Chris Chabris focuses on the fact that the results of his work, does not mean that the previous studies were not conducted properly. This is most likely on the intellect as well as growth depends on a whole set of genes (the height of a man due to the action of the cumulative effect of hundreds of genes).
Search for genes of intelligence, according to Chabris and promising areas of science, which can help to find relevant molecular pathways and neural circuits. Chabris said that he believes the search for genes end in itself, but as soon as something becomes aware of this gene, scientists can more closely relate psychological and biological concepts of intelligence. Answering the question of which gene is responsible for the transfer of intellectual abilities, scientists will be able to formulate a clearer and closer to answering the more important questions such as: "What kind of anatomical systems, these genes are involved?", "Where in the brain to produce proteins of these genes?" And "What is their evolutionary history?". The answers to these and other questions will give scientists a new key to understanding the mind.
For the study of intelligence at the genetic level scientists lack the aggregate statistics. According to Chabris sample should be 100 000 or more items to obtain objective data on this issue, because the psychological properties can not be determined by a single gene, such as Huntington's disease.
Scientists recognize that the work will be very time consuming, because one person had not the strength to grasp the understanding of the role of thousands of genes on a single process, but the level of science can make such a discovery at this stage.