A little saliva can test whether a child is a genius? Is the genetic test of the Internet celebrity really reliable?

In recent years, genetic testing has become commercialized and many people have tried it. Various genetic monitoring products have appeared on the market. Some genetic testing companies have launched "genius gene" testing packages, claiming that they can predict the upper limit of children's intelligence through saliva samples. Can we really use genetic codes to decipher the code of human wisdom?

Some genetic monitoring products claiming to detect talent

How does genetic testing for IQ work?

If you want to know whether this thing is reliable or not, you must first know how the merchants operate.

Generally speaking, if you purchase a genetic testing product, you will receive a genetic testing kit shortly afterwards.

The kit contains a small test tube, a cotton swab and some instructions for you to collect your own sample, which is saliva. The sampling is very simple. You just need to follow the instructions and then send the sample back to the laboratory.

Then the staff starts to process it. They will use extraction reagents to process the cells in the mouth swab to extract the DNA .

Next, the extracted DNA sample is amplified using the premixed PCR reaction solution in the genetic testing kit. This step is the core step of genetic testing, and its purpose is to amplify specific gene fragments related to IQ so that they can be observed in the test .

Generally speaking, businesses will choose a variety of genes related to IQ for amplification, such as COMT and MCPH1 genes (there are others, which are not introduced here). Among them, the COMT gene is related to the prefrontal cortex of the brain, which is closely related to cognitive control and emotional regulation ; while the MCPH1 gene is related to the development of the cerebral cortex, affecting brain volume and neural development . Mutations in these genes may affect the development of intelligence, so they have become key targets in genetic testing.

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

After PCR amplification is completed, the sample is analyzed using a fluorescent quantitative PCR instrument. Based on the judgment, the experimenter can determine the type of variation of the COMT and MCPH1 genes in the sample and derive a gene score. Ultimately, the genetic test report will combine the sample's gene score and provide an analysis of the genetic characteristics of intelligence.

Simply put, this method is to predict traits based on a single gene. This operation is relatively simple, and it can be described in one word: fast ! It mainly relies on PCR amplification technology to detect mutation sites of specific genes. Its goal is to directly identify whether there is a specific mutation in the target gene through DNA analysis, and to predict potential problems in learning ability through this single gene analysis.

Is it reliable for a single gene to predict certain traits?

The question is, is it reliable for a single gene to predict certain traits?

It can be said with certainty that this is unreliable . Because a single gene can only affect a small part of intelligence and cannot fully explain the difference in intelligence. The formation of intelligence is not controlled by just one or a few genes, but is determined by multiple genes and the interaction between these genes and environmental factors.

Taking COMT as an example, COMT genes include Val type (high activity type) and Met type (low activity type). Studies have found that the Met type may be associated with better working memory performance.

However, according to a study by Andreas Meyer-Lindenberg in 2005, the COMT gene Val158Met variant does have a certain effect on the activity of the brain's prefrontal cortex, especially in tasks that require high cognitive load. However, this effect is weak and mainly depends on the nature of the task and cognitive load, with almost no difference in low-load tasks. Studies have also shown that the interaction between genes and the environment plays a crucial role in cognitive performance . Therefore, the influence of a single gene is not enough to fully explain an individual's cognitive ability.

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

More than just single gene testing

Multi-gene testing is not reliable

Of course, some businesses will use multi-gene testing instead of single-gene testing. Simply put, researchers have found many genes related to intelligence (like puzzle pieces). The influence of each gene is like the size and shape of a puzzle piece. If a gene has a greater impact on intelligence, give it a larger score; if the impact is small, give it a smaller score. Then, add up the scores of all genes to get a total score, which is like the intelligence pattern you have assembled. The single gene mentioned above has an impact like only one piece of the puzzle. It seems better than the method used by the previous business.

But it turns out that the method of predicting IQ by polygenic testing is still not very reliable. In 2018, Savage's research results still showed that the explanatory power of polygenic scores was limited. The study used intelligence-related data from multiple large GWAS and integrated genotype data from different populations, with a total sample size of 280,000 people.

The results showed that the polygenic score can explain about 5% to 10% of the difference in intelligence , that is, through the genetic score, the researchers can predict a small part of the difference in intelligence between individuals in the population. This is a relatively small explanatory power, which means that although there are a large number of genes related to intelligence, the contribution of genes themselves is still limited.

The study also showed that about 90% of the differences in intelligence cannot be explained by polygenic scores . These differences are likely related to environmental factors (such as education, family background, socioeconomic status, etc.). This emphasizes the decisive role of the environment on intelligence and the importance of the interaction between genes and the environment in the formation of intelligence . Genes may provide individuals with a certain potential, but environmental factors also play a key role in the final expression of intelligence.

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

A similar view emerged in a 2021 study that found that although polygenic scores can predict the distribution of intelligence in a group, individual differences are large and cannot accurately predict an individual's intelligence level. In other words, genetic scores are not the determining factor of intelligence, but only part of many influencing factors.

In the 2003 Turkheimer study, the researchers proposed that socioeconomic status and environmental factors may play an important moderating role in the genetic influence on intelligence.

The researchers used a twin study design to analyze a sample of twins from the United States, including a pair of identical twins and fraternal twins. The researchers used twin samples because identical twins are very similar genetically, while fraternal twins have lower genetic similarities. Therefore, comparing the intelligence performance of these two types of twins can help distinguish the role of genetic factors and environmental factors in intelligence.

The study found that in high-income families, genetic factors dominate the influence of intelligence. In other words, in these families, intelligence differences are mainly determined by genetics. Data analysis shows that in high-income families, the contribution of genetics is as high as 60% to 70%, while the impact of the environment is relatively small.

In low-income families, the situation is quite different. Studies have shown that environmental factors have a much greater impact on intelligence than genetic factors. In these families, differences in intelligence mainly come from family and social environment, while the contribution of genetics to intelligence is significantly reduced. Data analysis shows that the contribution of the environment may reach 70% in low-income families, while the contribution of genetics drops to about 20%. The study emphasizes that in low-income families, the contribution of environmental factors may far exceed genetic factors. If more effective educational interventions can be carried out in the early stages of a child's growth, studies have shown that intelligence scores can be increased by about 15%, indicating that environmental factors can make up for the deficiencies of genes.

Judging from the current research results, genetic testing cannot accurately predict IQ . Although genes have a significant impact on intelligence, genetic testing can only predict part of the difference in intelligence, and the accuracy is still low. The formation of intelligence is the result of the combined effect of genes and the environment, and environmental factors play an important role in it. The plasticity of intelligence means that through education, social support and appropriate environmental intervention, the intelligence of an individual can be effectively improved.

Even if you have done a genetic test and received a test report, you should not regard it as a verdict of fate, but as a roadmap to unlock your potential. The true code of human wisdom is always written on the road of continuous breakthroughs in the pursuit of knowledge.

References

[1]https://patents.google.com/patent/CN101724687A/zh

[2]https://pubmed.ncbi.nlm.nih.gov/15809405/

[3]https://www.nature.com/articles/s41588-018-0152-6

[4]https://pubmed.ncbi.nlm.nih.gov/14629696/

Planning and production

Author: Su Chengyu, popular science creator

Reviewer: Ye Sheng, Professor of School of Medical Science and Engineering, Beihang University

Planning丨He Tong

Editor: He Tong

Proofread by Xu Lai and Lin Lin

The cover image and the images in this article are from the copyright library

Reprinting may lead to copyright disputes