At the dawn of the twentieth century, pundits predicted it would be the age of chemistry. To some extent, they were right as many of the basic advances we enjoyed arose from new chemical compounds – including antibiotics, nanotubes and polymers.
As we approached the twenty-first century, similar predictions were being made about this century being the age of biology or, more precisely, biotechnology. A couple of decades in, it is apparent DNA and genetics are taking hold as transformative technologies. We are beginning to see the world in a different way using different tools.
This was made apparent to me earlier this week during Adam O’Dell’s thesis defense. Examining the content of fish stomachs using advanced genetics techniques allowed him to determine the myriad of insects the fish had consumed. There were a lot of species present.
He was also able to examine the DNA content of the creek in which the fish lived. This gave evidence of an even greater diversity of organisms from invertebrates such as mayflies and mosquitos to plants and other organisms upstream. The fish he examined were only eating a subset of all of the available food.
More interesting, the stomach contents of the fish were different from year to year as were the DNA components found in the stream. We tend to think of the environment around us as static when it is a complex and evolving system. Just because a stream has one type of food insect one year doesn’t mean it will be there the next. Or, at least, it doesn’t mean it will be present at the same time the following year.
As a consequence, mapping a food web is a complicated process. It doesn’t help that the fish in Adam’s study appear to be facultative feeders consuming whatever they can get hold of. In a world where food is always in short supply, animals don’t tend to be picky eaters.
His work points out just how far we have come and just how important DNA is in modern biology, ecology, and environmental science. It is a marker for the species present and an indicator of the food web.
Outside of the cell, DNA does degrade over time but it can still be linked back to the species of origin. It is a fingerprint of the complexity of an environment.
It also pointed out just how much we don’t know. There are more unanswered questions about the environment than answered. And even some of the answers have to change over time as ecosystems are constantly changing.
At the same time as we are trying to understand the DNA around us we are looking inside are own cells trying to understand both our heritage and its function. An article in Nature this past week brings this into focus.
During the 1990s, much time, effort, and energy went into solving the human genome. It was considered one of the great scientific projects of all time, comparable in scope to landing a man on the moon in 1969.
In 2000, a draft of the human genome sequence was slowly being sketched and geneticists were betting on just how many genes we would have. But despite having the completed blueprint in front of us, the answer is still up in the air.
Initial estimates were on the order of 100,000 genes but the number quickly shrunk to something on the order of 30,000 as scientists began to read the code. The latest estimate puts the number of protein-coding genes at 21,306 while the number of non-coding genes is 21,586. Of course, these numbers have been hotly contested by other researchers claiming slightly different numbers.
The differences are, in part, a consequence of the techniques measuring the DNA but it also depends to a large degree on the definition of a gene. This has been evolving. The technical dictionary definition of a gene is: “a distinct sequence of nucleotides forming part of a chromosome, the order of which determines the order of monomers in a polypeptide or nucleic acid molecule which a cell (or virus) may synthesize.”
In other words, a gene is the unit of DNA giving rise to a protein. But over the past two decades it has become widely accepted our genome is much more complicated with genes affecting the operations of a cell which do not express a protein.
It is becoming more apparent complex traits such as eye colour or height are the result of a multitude of genes working together. Just how many and what they are all doing is still an open question.
Large scale ecosystems contain a complex interwoven web of life from the smallest microbe to the largest predators and plants. Turns out even the tiny ecosystem inside our cells is more complex than we initially thought it would be.
