Posts Tagged ‘Mitochondria’

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Biology of Gilgamesh

July 25, 2012

Considered to be one of the oldest stories, the Epic of Gilgamesh originated in Mesopotamia most likely based on a 2500BC King of Uruk, which is now modern day Iraq. I could summarize the story, but in this Star Trek episode, Captain Picard does a mighty fine job.

Gilgamesh, though most likely based on a real king, is supposed to be 2/3 god and 1/3 human. Though we cannot precisely determine why the legend would include such an odd detail, or what the people who passed this story down were trying to say, I was curious as to how someone could be 2/3 of something and 1/3 of something, genetically. I have a few hypotheses that I would like to discuss.

Mathematically, this is impossible.

Because Gilgamesh most likely was human, we can safely assume he had two biological parents, like all of us. So the question is, how could the union of two people produce a person who is 2/3 one thing and 1/3 another thing?

Let’s say a god and a human have a child. That child (N) will be 1/2 god and 1/2 human, making him not enough god.

If N1 then had a child with a god, the new child (N2) would be 3/4 god and 1/4 human, making N2 too much god.

If N2 then had a child with a human, he would be way too much human, but if he had a child with a god, he’d be way too much god. So what if N2 had a child with a child like N1 (1/2 god 1/2 human)? He would end up with a child (N3) that is 5/8 god and 3/8 human, which makes him not enough god.

Diagram of the limit as it approaches 2/3.

If we continue this pattern, of child N procreating with child N-1, we will never get a perfect 2/3 god 1/3 human, and that is simply because we are working with pairs. No power of 2 will ever come out to be divisible by 3.

Perhaps there’s a third parent.

When a man and a woman love each other, they can make a baby. While his sperm donates 22 chromosomes and a Y, her egg donates 22 chromosomes, an X, and mitochondrial DNA. So genetically there is inherently some inequality in the amount of genetic information passed down. Disregarding the fact that the X chromosome holds so much more information than the Y, which really holds just the male determining genes (the SRY), the woman is responsible for giving her child good mitochondria, because her eggs hold the mitochondria that the developing baby must have in all of its cells.

Mitochondria are the energy producing organelles in the cell, and they originate from bacteria that formed a symbiotic relationship with ancient cells. Because they used to be bacteria, they also come with their own DNA. Even though over the years a lot of the mitochondrial genome has been transferred into our genome, quite a few important genes are still made in mitochondria, such as mitochondria specific proteins and mitochondrial tRNAs.

Mitochondrial DNA is also implicated in many human diseases as a result of the important genes it has. As a result, many have considered the possibility of a therapy for these diseases; instead of the mother giving her genome and her egg which holds the mitochondria, the egg and mitochondria could come from another woman who doesn’t have a mitochondrial disease. But this sort of procedure is still really in development and requires legal work to be done.

But even if the ancient Mesopatamians did have the in vitro fertilization technology to do this, one god’s mitochondrial DNA is certainly not enough to give her equal credit to the god and human that gave half their genomes.

Polyploidy

Though we are all diploid organisms, or organisms that have two copies of each chromosome with one coming from each parent, there are strange cases of having extra copies of chromosomes. The two most famous being trisomy of chromosome 21, which leads to Down Syndrome, and Kleinfelter’s Syndrome, which is where a man has 3 sex chromosomes: 2 X chromosomes and a Y. Unfortunately, these are the most well known because they are the only ones that are mild enough to lead to live births, any other kind of trisomy leads to death and miscarriage.

But these are just trisomies, where there is just one extra chromosome. Triploidy, or having three sets of each chromosome, definitely does not lead to a live birth, usually ending in miscarriage. These embryos come from either the egg or the sperm not properly dividing and thus still being diploid and not haploid. But the reason these embryos cannot develop is because there is just too much genetic information for the babies to handle. And in many cases, there are genes that we actually only want to have one active copy. Many of genes are called imprinted genes because only the mother or only the father’s gene is usually active.

So this is definitely not a reasonable explanation for Gilgamesh’s 2/3 god and 1/3 human genetics, but it does come the closest. If Gilgamesh’s godly parent donated twice as much DNA as the human parent, and he was still able to develop, then this could work. He would still have two parents, but his triploidy would make him genetically 2/3 god and 1/3 human. And who knows, maybe Gilgamesh’s godly genes have special proteins that can deal with the extra genetic information.

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Biology of Cyclops (X-Men)

July 12, 2012

I thought it would be fun if in this blog, I tried to figure out, hypothetically, how different superhero superpowers could work, biologically. Obviously, I can’t do a lot of superpowers because they are just so fantastical that there really would be no basis for a biological explanation (such as Storm’s ability to control weather, though if you think there is a way, please tell me!). But a few superpowers may be kind of fun to think about how that could actually happen, and though the topic of today’s post is a huge stretch, considering how it could work might teach us a little about biology.

Cyclops, whose real name is Scott Summers, is a leader and one of the founding members of Marvel’s X-Men. Though I have read a lot of comic books, I certainly don’t have a complete and extensive knowledge, so some of the descriptions of his powers are based on what I have read, seen on many movies and animated cartoons, and read on wikipedia.

The Superpower.

Called the “optic blast,” Cyclops has, what many may consider a disability, the power of shooting beams of high energy light from his eyes constantly. Though these beams are illustrated as red beams, this is most likely an artistic rendering of a much more powerful electromagnetic radiation than just red light. (Can you imagine how lame it would be if his power was just his eyes glow really really brightly red?) His optic blast is said to not give off any heat, as well as not have any kind of recoil effect (meaning shooting the beams doesn’t push his head backward, which makes sense because otherwise he’d constantly feel his head pushed back). His power as well as his own life depends on sunlight, with him getting weak and even losing the optic blast after prolonged time in darkness. The comics describe him having the ability to metabolize sunlight and even little amounts of energy that surround him.

He is also immune to his own power, meaning though his beams can hurt other people he doesn’t feel any pain, thus allowing him to be able to close his eyes with no eyelid damage. Additionally, his brothers Havok, or Alex Summers, and Vulcan, or Gabriel Summers, have similar powers where they can use light and ambient energy and change it in different ways, though Vulcan probably has the strongest amount of control. Interestingly, while Cyclops and Havok are immune to each other’s beams, neither are immune to Vulcan’s, and Vulcan is not immune to Havok’s, which is very strange.

Note: I thought I would try to cover a biological basis of ALL of Cyclops’ powers, but I only ended up really getting at one. Stay tuned in the future when I try to tackle more!

Metabolizing the Sun’s Energy.

This is definitely not a foreign concept. You may have heard of the organisms on our planet that can convert light energy into chemical energy. They are called plants, and they use photosynthesis to do this everyday. Photosynthesis occurs in a special part of their cells called the chloroplasts, and these chloroplasts are little membrane sacs that are filled with chlorophyll, which does the action of using light energy to split water into protons (H+), oxygen (O2), and electrons. These electrons are high in energy, so the chlorophyll convert that energy into usable chemical forms of energy, like ATP and NADPH.

Photosynthesis is a crucially important biochemical process for life on earth as we know it. Animals, a group in which humans are included, cannot convert light energy into usable energy, instead requiring energy from their diet. That energy naturally comes from plants. But I must note that plants, like trees and flowers, don’t contribute to the majority of photosynthesis on the planet. The algae and the cyanobacteria in the oceans contribute most of our planet’s photosynthesis. So you should really thank these single celled organisms for all the oxygen you breathe in. Cyanobacteria don’t have chloroplasts, but instead just have the chlorophyll and thus the capability to do photosynthesis. Additionally, scientists have discovered that plants’ chloroplasts are the result of ancient cyanobacteria going inside and living harmoniously with ancient cells (endosymbiosis), and they slowly evolved to be dependent on each other. (The evidence for this lies in the fact that chloroplasts have their own DNA, which is very similar to cyanobacteria DNA).

How Humans Could Get this Power.

So the ability to turn light energy into chemical energy is not necessarily a superpower as it is seen in the natural world. But for a human to be able to do it is remarkable. There are a couple ways I can think of in which Cyclops could have been able to biologically get this ability.

1. He could have spontaneously had a few random gene mutations that turned a few genes he had into genes that are photosythesis-like genes.

2. He could have had some strange endosymbiotic event while he was an embryo that led to a photosynthetic organism becoming part of his physiology.

The first of my ideas are completely implausible. It would be to say photosynthesis was created in a day. Though photosynthesis does require the use of a few proteins we have in the animal world, namely the electron transport chain which we have in our mitochondria (as do plants in their mitochondria), the shear number of other proteins that would be required to spontaneously appear in his biology would be impossible.

Additionally, the fact that his brothers also have the ability to metabolize sunlight makes the likelihood of this spontaneous generation of photosynthesis implausible. Though in the comics his parents don’t have any superpowers, making that impossible.

But the more likely explanation is the second way. Instead of having all the right mutations to be able metabolize light, perhaps at an early embryonic stage, his cells absorbed some bacteria that could do photosynthesis, and thus gave him the ability. If this were the case, then that means the real mutation was in his mother. One option is that his mother had some kind of maternal effect gene that causes her embryos to absorb cyanobacteria and enable a mutualistic relationship. This is an attractive idea because that would mean she would have had a mutation that would not result in a phenotype for her, aka she can give her children powers, but she has none. Another option is if she had the ability/bacteria, then she would have passed down the bacteria in her eggs. But this is unlikely because she would have known she had this ability. Note that in either case, the father doesn’t matter, because the embryos don’t develop inside of him so he can’t give them anything special during development, and he only donates sperm which does not pass down things like mitochondria or other organelles, just DNA. This theory is supported by the fact that none of Cyclops’ children (Cable and Rachel Summers) can absorb and use sunlight, instead all inheriting abilities more similar to their mother Jean Grey.

Metabolizing Ambient Energy.

Finally, the more intriguing thing about this power is that they can absorb and use ambient energy, or as I interpret it, any kind of extra heat energy given off from any number of sources that just flows out into the environment. Thermodynamically, this sort of energy is usually thought of as energy that cannot be recovered. Though I don’t believe any organism is known to be able to capture this kind of energy, if something could, that would be a huge development. So here is where the biology sort of escapes me, and this ability to absorb energy really does become a superpower.