More than 60 years ago Francis Crick and James Watson discovered the double helical structure of deoxyribonucleic acid known as DNA. Today, for mere pennies you can sequence their own DNA and learn about your ancestors and problems. However, although the transmission of DNA from parents to children is the biological Foundation of heredity, we still know relatively little about the specific genes that make us who we are.
The situation is changing rapidly, thanks to the research of genomics — briefly their Association called GWAS (genome-wide association studies). These studies are looking for differences in the genetic composition of the people — their “genotypes” — that correlate with differences in their observed characteristics, their “phenotypes”. In a recently published GWAS in Nature Genetics, a group of scientists from around the world analysed the DNA sequence 78 308 people in search of correlations with the General level of intelligence, measured by IQ tests.
The main objective of the study was to identify single nucleotide polymorphisms or SNP that significantly correlated with tests of intelligence. DNA, which is present in most cells throughout the body, consists of four molecules, called nucleotides, which are denoted by their organic base: cytosine (C), thymine (T), adenine (A) and guanine (G). Within cells DNA organized into structures called chromosomes. Humans usually have 23 pairs of chromosomes, one in each pair inherited from each parent.
Single-nucleotide polymorphism, SNP (or “SNiP”), is a nucleotide in a specific area of chromosomes, which can differ among people. For example, one person may have a nucleotide triplet tats and the other TCC, and this may contribute to the manifestations of differences between people in such traits as intelligence. Genes are composed of much longer nucleotide sequences and act as instructions for creating proteins — the basic building blocks of life.
Of more than 12 million analyzed SNP, 336 largely correlated with intelligence, assuming 22 different genes. One of the genes involved in the regulation of growth of neurons; the other is associated with mental incapacity and cerebral malformation. In total, the SNP accounted for about 5% of differences between people in intelligence is two times more than shown by previous GWAS in the field of intelligence. In total, scientists have identified about 30 genes associated with intelligence.
Checking replenishement their results, researchers tested the correlation between 336 SNP and level of education — a variable that is highly correlated with intelligence — in an independent sample of nearly 200 000 people, who have previously undergone DNA testing. In 99% of cases SNP correlated with education in the same extent that it correlated with intelligence. This conclusion helps to resolve fears that the SNP associated with intelligence, gave a false result is to remove the randomness. The authors concluded that the results “provide a starting point for understanding the molecular neurobiological mechanisms that control intelligence, one of the most studied human traits”.
Of course, intelligence can not be called purely the product of DNA and no scientist investigating the intelligence will not be thinking about that. The environment has a strong influence on the development of intelligence or any other psychological traits. At the same time, knowledge obtained from research in the field of molecular genetics may one day be useful to identify children with risk of development of serious intellectual deficiencies and for which early intervention can reduce the risk. This study also provides scientific basis for understanding how to manipulate the brain to enhance intelligence.
Neurobiological studies of the pillars of intelligence and other psychological traits of fanning heated debate on the topic of “heredity or upbringing” and at the same time can end them. We are a product of their environment and genetics, the close relationship of both. Research that will lead to a better understanding of the game, will provide scientists a deep understanding of the similarities and differences of our psychological structure.