The fission

Version française : Steemit | Busy

What means this title? I put this title to explain you, bacteria reproduction. Yes, bacteria reproduce them by fission, this is an asexual reproduction, that, means that they don’t need a partner. Strange no?

Indeed, the father individual becomes two child individual which are the same between them and with the father individual. In sum, these are clones, with the same genetic information (the same DNA coil in the two child individuals).

But then, how DNA has one copy in each cell/ bacteria?

You said it! One copy of each individual, that imply that DNA “clone itself”. This phenomenon is called DNA replication, it’s an important process (there will a chronicle on this).

That’s all for bacteria reproduction!

Rigorously we can't say that it’s a reproduction in the term strict sense.

Yes, we talk about reproduction when there is a genetic mixing (genome modification). Mmmmh that’s true when we think about that…

How a bacteria which divide itself (which clone itself roughly) changes his genetic code in order to evolve?

Let’s discuss bacteria evolution, how they change their genomes?

First, there are mutations, they occur during the DNA replication, eh yes, this mechanism is not perfect. There may is an error in the copied genetic sequence; an A becomes a T, a G becomes an A, …

Then there are genetics recombination, this phenomenon is in the same register than mutations. This is also the fault of DNA replication (decidedly), in this case, this is outright a part of the sequence which changes his place in the genome. Father and Child will have different sequences but with the same amount of A, C, T and, G. You follow me?

Consequently, these mutations or recombination change coded function in DNA (one base mutation can fully shut down a gene working, or don’t have an effect). Evolution generated by these two phenomena is chancy, because it’s the result of an error, besides it’s a very slow evolution. Indeed, novel function acquisition needs a big amount of generations. Is like finding a word at Scrabble with blinded eyes.

And if you can’t find a word at Scrabble you, generally, pick letters (even the full word) to your neighbor. Bacteria are also cheaters!

That is called lateral gene transfer, as his name indicates it’s a gene transfer from a bacteria to another. The lateral adjective is opposed to vertical which is simply from father to child. Lateral gene transfer allows a faster and oriented evolution.

This phenomenon can be achieved by 3 ways:

The bacterial conjugation: two bacteria of the same species link them to transfer a small DNA piece, generally it’s a plasmid. Of course, the giver keeps a copy and the receiver checks if he has already this DNA piece (have in double is useless). It’s a high energy process but the two bacteria stay alive.

The bacterial transformation: have you already find something in a bin? Never for me… The transformation is the acquisition, by a bacteria, of a DNA piece find on dead bacteria.

Transduction: gene transfer by a virus, virus infect the bacteria but integrate a DNA piece from his. During the virus propagation, he carries out the DNA piece from the bacteria and could transfer it to another bacteria which will infect. Who manipulate who in this story?

Of course, I will go back on these strange things that are viruses.