Horizontal Gene Transfer in Humans

For the past few decades genetically modified (GM) crops across the World were meted with lot of resistance from green activists. Wide spread campaigns strongly denounced GM crops as monster crops. They enunciated that their cultivation would destroy the traditional agriculture and decimate human race. The pseudo-science and superstition has resulted in curbing of field trials in India. The uproar and activism against these crops pressurised the government to act against the GM crops. While several acres of land is under the cultivation of GM crops in the US but the Europe shied away from its cultivation and enforced a strict ban on all the GM crops products. Research carried out by scientists in Cambridge University shed new light on the gene transfers annihilating fears about the cultivation of GM crops.

Fundamentally genes or the hereditary material DNA is transmitted from parents to the offspring directly through vertical gene transfer. There are reported instances of alternative mechanisms of gene transfer, know as horizontal gene transfer or lateral gene transfer reported in bacteria and unicellular eukaryotes. Existence of such mechanism is not established in higher organisms like vertebrates and least known in humans. Against this back ground, the research article published in Genome Biology by Alistair Crisp and Chiara Boschetti made startling observations indicating that humans have obtained 145 genes from their ancestors. Though it is much less than 1% of 20,000 human genes it is surprising to learn that human have obtained genes from lower organisms like flies, nematodes, fungus, plants and bacteria. The classical example of Drosophila obtaining more than 1Mb of genome from Wolbachia, a bacterium indicates that HGT is very common in lower organisms.

HGT involves transfer of the genetic material between different organisms and this process has played a crucial role in acquiring antibiotic resistance in bacteria. Genes obtained by HGT are mostly associated with metabolism and code for enzymatic activity suggesting that the process contributes to biochemical diversification. Computational analysis of transcriptomes of 40 different species carried out in this paper concluded that HGT occurs at low but in appreciable levels across all animal species. It has occurred over a period of time and still continues to occur and that it originated from bacteria and Prostists. In spite of structural complexities, research shows that overall levels of HGT are not conspicuously different between vertebrates and invertebrates.

While analysing the transcriptomes (data base of the mRNAs) comparison with immediate relatives is avoided. Flies are not compared to arthropods similarly no vertebrates with primates and no nematodes with worms. The results yielded that worms had 173 HGT genes, flies 40 and primates 109. It is interesting to learn that the genes responsible for the ABO antigen system which is the basis for blood groups is bacterial in origin and the genes involved in the synthesis of the hyaluronic acid, is from fungi and the gene associated with obesity has migrated from marine algae suggesting that gene insertions played a vital role during the process of evolution.

The human genome deciphered in 2000 also suggested the presence of plant genes. But it raised severe flak from critics who enunciated alternate theories to account for those genes to gene loss, convergent or divergent evolution. Researchers now comprehend that 1% of human genome might have immigrant from different species. Scientists who are attempting to create GM crops are just invoking the process that happened in nature over a period of time. During the course of evolution, foreign genes integrated into humans which slowly began to cohabit with its genome. Activists are now rallying behind the point that natural gene transfers took place over centuries. But it has to be borne in mind that even during the natural transfers, these genes were as align as the Bt gene insertion into cotton or brinjal. In fact scientists are simply replicating the process of natural gene transfer in a controlled environment in the laboratories to obtain GM crops. To ensure complete integration of foreign gene, scientists grow these crops under strict supervision and protected environment before releasing it for commercial use. Strict regulations and checks are in place to ensure minimal gene contamination and release into the environment.

This robust research now strongly questions the stand point of the green activists who demand complete annulment of GM crops. Besides allaying the fears of common man, the paper mocks at the frivolous scientific guidelines patronised by the antagonists of GM crops.