The completion of a South American lung fish genome sequencing represents one of the most remarkable moments within current genetic research. Because of its 91 billion DNA base pairs, it has now officially been confirmed that this genome has fully decoded, the largest animal genome heretofore achieved by human genetic engineering, thirty times larger than a human genome. It has long fascinated genetic researchers for decades because of what lung fish symbolised: they are among the closest living relatives to the first vertebrate creature to emerge from water onto land. Today, what its genetic makeup has revealed allows a glimpse of a new post-genomics age for future research on evolutionary aspects of genomes for the first time ever.
Advanced genome sequencing technology unlocks the South American lungfish’s 91 billion base pair DNA
The genome was large enough that it would have taken a long time and many resources to sequence with a mere DNA sequencer, as it was very dense with repeated regions. This meant it was necessary to use one of the latest types of DNA sequencers, ones that can read very large sections of DNA at a single pass. This was also accompanied by software powerful enough to take an enormous amount of DNA fragments and piece them together to form a complete genome, showing how long it would take for such a technology to be achieved.While the lungfish’s genome boasts a staggering 91 billion base pairs, this not only makes it larger than the human genome, it also makes it the largest genome of any animal ever sequenced. Notably, this enormous size doesn’t correlate to an enormous number of genes but rather to repetitive regions within its genome. In fact, some single regions within the lungfish’s genome are larger than the human genome, indicating that the evolution of larger size doesn’t necessarily entail the evolution of more genes.
What the lungfish genome reveals about DNA and complexity
One of the most valuable teachings of this finding is that genome size does not function as a reliable measure of the complexity of an organism. A human, a lungfish, and most vertebrates actually possess a similar number of functional genes. However, varying levels of additional DNA exist in these species. In lungfish, there is a staggering expansion of repeated elements and non-coding DNA. This supports that a large piece of DNA is involved in either a regulatory, structural, or as yet undefined function rather than a protein-coding function.
The lungfish genome and the origins of land animals
In South America, the South American lungfish, otherwise known as the living fossil, “Lepidosiren paradoxa,” appears to remain unchanged after hundreds of millions of years. Lungfish are found in slow-moving rivers and swamps in South America, where they can survive conditions by breathing air and estivating, which is a state of dormancy, especially in the dry season. Again, this is very much like conditions that vertebrates may have survived in after transitioning to life on land. Analysis of the genetic makeup of the lungfish enables researchers to look at ancient genetic traits that have been maintained since the time of the early amphibian, reptilian, avian, and mammalian groups.The lungfish has a very important place in the evolutionary tree, and this species was very close to where vertebrates made their transition to land. The genome of this fish has yielded many important answers for scientists regarding how these fish made their transition to land, ranging from respiration to limb development. By comparison of lungfish genome sequences to other vertebrates, scientists can determine which parts of their genomes are more ancient than others.
