Groundbreaking Discovery: Plant and Human DNA Interaction Image Credit: S Saraus/Shutterstock
How crucial is our genome? While some researchers argue that most of our DNA is active and thus essential, others suggest that even random DNA could show high activity levels. Current studies focus on human cells that incorporate substantial segments of plant DNA, shedding light on this topic. According to New Scientist, the largely random plant DNA exhibits nearly equal activity to human DNA.
This research indicates that much genomic activity may lack purpose, further supporting the theory that a significant portion of the human genome is ‘junk DNA.’
“Most activity can be attributed to background noise,” says Brett Aidy, a researcher at the University of Auckland, New Zealand. “This aligns with the concept of junk DNA.”
The primary role of DNA is to encode instructions for protein synthesis, which are essential molecular machines responsible for cellular functions. This genetic blueprint is transcribed into messenger RNA, which transports the instructions to ribosomes, the cellular machinery for protein production.
Previously, it was assumed that nearly all DNA was involved in coding proteins, but now we understand that just 1.2% of the human genome directly encodes proteins. What, then, is the destiny of the remaining DNA?
Since the 1960s, biologists have claimed that much of it is unproductive. While it’s true that some non-coding DNA plays vital roles, ongoing discoveries of functional elements won’t redefine the overarching notion that non-coding DNA is largely inert.
For instance, a 2011 study revealed that: only about 5% of the genome is evolutionarily conserved. Evolution appears indifferent to the rest. Proponents of the junk DNA theory highlight the variability in genome sizes among species. Why, for example, does an onion require five times more DNA than a human? Additionally, why do lungfish possess genomes that are thirty times larger?
In contrast, other scientists explore whether human DNA has functional roles, even if converted RNA lacks known applications. The ENCODE project’s 2012 findings suggest that over 80% of the human genome is active in some form. This raised questions about its classification as junk DNA. Some researchers have coined the term “dark DNA” for non-coding regions whose purpose remains unclear.
In reaction to ENCODE’s claims, in 2013, Sean Eddy from Harvard University proposed a controversial random genome project, hypothesizing that injecting synthetic random DNA into human cells would yield similar activity as noted in ENCODE’s findings.
“If this holds true, the results will call into question the interpretation of activity as indicative of functionality,” he posits. Austin Ganley, also from Auckland University, echoes this sentiment, emphasizing the need for baseline comparisons in the research of functional versus non-functional DNA.
However, synthesizing DNA is resource-intensive. So far, only limited attempts at random genome projects have focused on small DNA segments.
Yet, when Adey and Ganley discovered that Japanese researchers had successfully created human-plant hybrid cells with DNA segments from Thale cress (Arabidopsis), they recognized it as potentially the most extensive random genome experiment to date.
Eddy, though not directly involved, acknowledges the significance. Plants and animals diverged from a common ancestor over 1.6 billion years ago, allowing time for random mutations to accumulate within non-coding DNA segments of Arabidopsis.
Following initial validations that plant DNA behaves as random DNA in human cells, Adey and Ganley assessed DNA-to-RNA conversion rates per 1000 base pairs of non-coding DNA. If DNA to RNA conversion implies functionality, plant DNA should minimal undergo this transformation. Surprisingly, they observed slightly less activity—about 80% of the starting sites per kilobase when compared to human non-coding DNA from Arabidopsis.
This strongly indicates that the genomic activity detected by ENCODE is merely background noise.
“This illustrates the inherent noise in biological systems,” comments Chris Ponting from the University of Edinburgh, UK. “This sequence’s biochemical activity holds no function within human cells.”
“Sophisticated investigations like this were essential,” asserts Dan Graul from the University of Houston, Texas. “This adds experimental evidence confirming the long-held belief that a majority of the human genome is unnecessary. The term ‘dark DNA’ is simply a fantasy created by those envious of physics.”
Although imperfect biological systems produce noise, this noise can lead to beneficial variations that natural selection may target, notes Ganley.
The research team remains puzzled about a 25% increase in human DNA activity. “We still need to investigate the cause behind this finding,” Ganley states.
While some additional RNA generated might serve functional purposes, this does not diminish the overall perspective of junk DNA. Ongoing research is employing machine learning techniques to identify potentially meaningful activities amidst the noise.
The research team intends to publish their outcomes, though they have yet to complete their findings.
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Source: www.newscientist.com
