August 2012 : Page 2 of 2 : Proslogion

In a previous post, I discussed alternative splicing, an amazing aspect of our DNA that allows it to store information in a compact, elegant way. In brief, a gene is actually a recipe that the cell uses to make a particular protein. Since most of a cell’s DNA is in the nucleus, the “recipe” stored in that gene must leave the cell’s nucleus in order to be turned into a protein. To do that, the “recipe” is copied by a molecule called messenger RNA (mRNA). The mRNA then takes the copied “recipe” out of the nucleus to the ribosome, which is where proteins are made.

In eukaryotic cells (the kinds of cells found in plants and animals), however, something very interesting happens before the mRNA leaves the nucleus. Some parts of the mRNA are cut away, and the remaining parts are then stitched back together. The parts of the mRNA that are cut away never leave the nucleus, so they are called introns (they stay IN the nucleus). The remaining parts that are stitched together are called exons (they EXit the nucleus). For a while, geneticists didn’t know the purpose of introns, so in typical evolutionary fashion, many decided that they had no purpose, and introns were lumped into the category of “junk DNA.” Of course, as we have learned more about genetics, we have learned that the evolution-inspired idea of “junk DNA” is, itself, junk, although some evolutionists still cling to it.

Nowadays, of course, we know the reason that introns exist. It is part of the design of the Creator, allowing DNA to store information in an incredibly efficient way. Each exon represents a “module” of useful information. If the cell stitches the exons together in one way, it makes one protein. If it stitches the exons together in another way, it makes a different protein. As a result, a single gene can actually produce many different proteins. The introns not only serve as a means by which the cell can identify the exons, they also regulate the amount of the various proteins that are being made.

This process of alternative splicing is illustrated in the figure below:

alt_spice — Because of alternative splicing, a single gene can tell the cell to produce different proteins. (public domain image)

In the previous post about alternative splicing, I discussed how recent evidence suggests that up to 95% of the genes in the human genome participate in this process. However, I did not address how many different proteins a single gene can produce using alternative splicing. In some cases, the answer is truly astounding.

Continue reading “One Gene = One Protein? Not Even Close!”

Over two years ago, I wrote about an interesting three-way mutualistic relationship between a virus, a fungus, and a plant. Less than a year later, I wrote about how people are actually walking ecosystems, participating in a huge number of mutualistic relationships with many different species of bacteria. Last night, while reading the scientific literature, I ran across another example of a three-way mutualistic relationship, and it is equally as fascinating!

This three-way relationship starts with seagrasses. Coral reefs are the “stars” of the marine world, but seagrass communities can be considered its “workhorses.” While they make up only 0.2% of the ocean’s ecosystems, they produce more biomass than the entire Amazonian rainforest!¹ Why are they so productive? Because they form a wide variety of marine ecosystems that serve as nurseries for many developing fishes and homes to a wide variety of sea creatures including turtles, manatees, shrimp, clams, sea stars, etc. Because of their amazing ability to support such ecosystems, seagrasses have been studied by marine biologists for some time. However, there has always been a nagging mystery associated with them.

The roots of seagrasses trap sediments which form a rich mud that is often several feet deep. The mud is rich because it contains all manner of decaying organic matter. However, the reason the organic matter decays is because bacteria decompose it. One of the byproducts of this bacterial decomposition is sulfide, and if that sulfide were allowed to build up to high concentrations, it would actually end up harming the seagrasses themselves. However, it never does. No one has proposed a satisfactory explanation as to why this doesn’t happen.

Certainly, the seagrasses transport oxygen to the mud through their roots, and that oxygen can turn the sulfide into sulfate, which is harmless to the seagrasses. However, detailed studies show that the sulfide produced by the resident bacteria accumulates far faster than it can be removed by the oxygen that is added to the mud through the seagrasses’ roots, especially during warm seasons.² Thus, there must be some other way that sulfide is being removed from the mud.

Marine biologists had no idea what this other way was…until now.

Continue reading “Another Example of Three-Way Mutualism. Is This Just the Tip of the Iceberg?”

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