Envisioned Universe

March 5, 2012

Animals that breathe oxygen use a process called oxidative respiration to get their energy from the food they eat and respire or breathe out water vapor and carbon dioxide.  Oxidative respiration is a hallmark for all complex animal life, but there are many evolutionary steps between the advent of the first life form that breathes oxygen, which was singe-celled and the first true animal life, which might have millions or even trillions of cells.  Before the first animals could appear on Earth, a highly organized and complex system responsible for governing an organism’s growth and development was needed to make sure that all of an animal’s cells were arranged in the proper place.  Imagine a fruit fly with feet on its head, and this should give one some perspective about the importance of the genes that regulate growth and development in animals.  The growth and development of organisms is controlled wholly by a specific set of genes and how these genes are activated is a process called gene expression.  Gene expression is of paramount important for eukaryotic organisms because of the sheer complexity involved in the development process.  Single-celled prokaryotic organisms don’t need the same tightly-regulated mechanisms that are characteristic of eukaryotes, but when trillions of cells need to be organized in a coherent way, these genes must be able to step up and complete the task.

All animals on Earth share certain key characteristics, like the ability to use oxygen in respiration mentioned earlier.  To start, because all animals are eukaryotic, the DNA is contained within the nucleus of cells so the process of replicating DNA, called transcription, occurs within the nucleus.  In addition, the process of replicating proteins, called translation, occurs mostly in ribosomes, which are organelles found in the cytoplasm.  Compared to prokaryotes where the process of translation and transcription occur in the cytoplasm, eukaryotes undergo translation and transcription separately.  This is important for eukaryotes because by segregating these two processes, both translation and transcription become more efficient.  This is especially important for eukaryotic organisms because the genome of eukaryotes can be 10 to 100 times larger than the prokaryotic genome.  The DNA of eukaryotic cells is loaded with transposons.  Transposons are repetitive sequences of genetic material that are able to move a transposase gene around within the genome.  Transposase allows the DNA to loop around itself and cut off a piece of the genome and relocate itself somewhere else within that strand of DNA.  Wherever it lands, the excised transposon disrupts the function of the gene that was occupying that stretch of the DNA.  So transposons help to regulate when and where and how which of our genes function at any given time.

Our Areiosan life uses all of the same steps for genomic expression that Earth life does, but different proteins are responsible for regulating genomic expression because our hypothetical life would have evolved on a different world and would have been subject to a completely different environment.  A typical eukaryotic protein-coding gene is surrounded on both sides by what are called a promoter and terminator sequence.  A promoter sequence is located upstream of each gene and serves as the sign that identifies that particular gene to the enzymes that will latch onto to it.  The terminator sequence appears at the very end of the gene and marks the point on the DNA were an enzyme should stop coding and signifies where a certain gene ends. DNA is made up of two different kinds of sequences; sequences that code for a certain gene and sequences and don’t code for a certain gene.   Noncoding sequences within DNA called introns.  They appear on the DNA in between segments responsible for coding proteins.  The sequences of genes that are responsible for coding proteins are called exons.

The similarities that pop up between my Areiosan gene expression and Earth gene expression are twofold. One, I don’t have an advanced degree in molecular biology, biochemistry, or genetics, so the thought of making up a brand new system of gene expression is a daunting task, and I thought it would be best to go with what I knew, which was how this works on Earth. And second, I like the idea of unifying life. Even in an imaginary world that I made up, it’s comforting to envision similarities, especially with the creatures that I designed to be so alien to begin with. One thought that has been hanging around my subconscious for a while came from a physicist Lawrence Krauss:

“Every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand. It really is the most poetic thing I know about physics: You are all stardust. You couldn’t be here if stars hadn’t exploded, because the elements — the carbon, nitrogen, oxygen, iron, all the things that matter for evolution and for life — weren’t created at the beginning of time. They were created in the nuclear furnaces of stars, and the only way for them to get into your body is if those stars were kind enough to explode…The stars died so that you could be here today.”

I’m comforted by the thought that if we were to ever meet intelligent aliens out there in the universe, the first thing that I would want to convey to these aliens would be our bodies (if these aliens had bodies) could very well be comprised from atoms expelled from the same star over four billion years ago. I would express awe that on the most fundamental level, our atoms are a part of the same cosmos, inanimate and incapable of any sentient thought, but that through evolution, these atoms were arranged in such a way that in this form they had been incorporated into beings not only endowed with reason, compassion, and empathy, but that for the first time in the history of the universe, the cosmos found a way to meditate onto itself and contemplate its own existence.