Variety is the spice of life II

Imagine a bacterium whose only mode of reproduction is binary fission (it splits itself into two). And then the process goes on and on. All the offspring are clones. You’d expect zero variation in their DNA, and hence in their appearance and function.

Pretty dull huh? Not only that, but this population would be doomed. With only one allele of every gene, ALL of them will either be resistant to certain antibiotics, or NONE will. So, antibiotic comes around, and there is a 50% probability the population will survive. Throw in 100 antibiotics and 10 different environmental pressures, and the population is good as dead.

Good thing for them that that’s not the case, that is, not all individual bacteria have identical DNA. How is that possible, since they reproduce by binary fission?? In fact, it is mind-opening just how many different ways they have of achieving just that: variation. Some are:

1. Conjugation. One bacterium produces a mating bridge through which a plasmid (circular piece of DNA) can pass to another bacterium.

2. Transformation. Bacteria can take up DNA from dead bacteria and use it as their own.

3. Transduction. Viruses which enter bacteria may pick up some of their DNA and pass it to the next bacteria they infect.

But none of these actually explain the CAUSE of DNA variation itself. By far the biggest cause of DNA variation in bacteria is, of course, mutation. One might say mutation is the inevitable effect of the very way DNA replicates, perhaps not a mistake, as it is often perceived, but as crucial a part of the overall process as the multitude of enzymes which take part. Just because it defies our (designer?) expectations of rigid rules that are never broken, doesn’t mean it is not integrated in nature as obviously as the pairing of DNA nucleotides is.

In fact, imagine a world without mutation and variation. Can you?

Comments

4 Reasons Google's Calico Won't "Solve Death"

The on-line world has been taken ablaze by Calico's bid to end ageing, and thus death itself, but is this what they will actually focus on, and will they achieve it? The fact is ageing will be reversed, and death by "natural causes" will go with it. The questions are "When?" and "By whom?". Until recently, not a lot was known about the approach Calico would take in this venture dubbed "moonshot thinking" - a term touted by Google as the source of all considerable human progress throughout history. This we don't doubt, but is this what Calico is all about? CNN's Dan Primack has revealed details about Calico's plan , which hint at a less-than-moonshot thinking approach, and cast a serious question mark on its ability to deliver the punchy TIME headline. Here is why: 1. The man with the idea, Bill Maris, arrived at the conclusion that the root of all death-causing disease is simply ageing itself. Not only is this widely

The evolution of the human body

In order to be able to look at ourselves in the mirror and be able to answer the question "Why do I look like this?", we must look back to our ancestry and their lifestyle, over a very long period of time. For the purpose of this analysis, let's look at the human versus the neanderthal. Recently there have been found neanderthal genes within the human gene pool, but the two species are different enough to compare, yet not too different (human versus fly would be too different). As you can see, the construction of the human pelvis and toes is different, and the human has less hair. This results in humans being able to run easily for long distances, in the detriment of short-distance running which we are worse at. We sweat better, so we can do more long-term effort. This feat is essential to better settlements, as we can discover a larger area with potentially better resources. It might seem counterproductive to not be able to run quickly for a short period, when it come

How do you experience evolutionary selection pressure?

Evolutionary selection permeates the consciousness of members of a species at a level higher than the individuals themselves. Everyone comes into awareness about the selection pressures and adaptations taking place across their population. This happens independently of who they happen to be. Awareness of “life”, being alive, what it takes to survive, exist in each individual even when they lack it in some perceived manner e.g. being unattractive, having low self-esteem, being a failure. Indeed, it’s what enables self-deprecation and sometimes suicide based on some of these beliefs in an individual. Each individual is not out for themselves, with the selection pressure encouraging them to succeed, but rather they are out for the collective they are part of, whether they realise it or not, whether they like it or not. It is detrimental to individuals to feel bad about themselves. However, this is the effect of collective selection. Individuals therefore place themselves

Principles of Evolution

Search This Blog