Friday, November 13, 2020

Polycistronic mRNA

Polycistronic mRNA is a rather interesting gene. It allows organisms to have multiple proteins encoded by one long RNA strand, showing the complexity of life at its finest. Having many genes acting in unison makes it possible for the organism to respond quickly and appropriately to changes in its environment.

But then again, it isn't so great. The organism is relegated to the creation of one protein at a time; and as an RNA strand containing many genes, it takes longer for the newly made protein to be translated from its initial form into a functional product in order for the cell to use it.

It is also quite complicated, as the RNA strand has to be decoded and then translated in order for it to become a functional protein.

Life is a balance of advantages and disadvantages. Polycistronic mRNA has its perks, but it also has its drawbacks which make life interesting.

The following is a list of the base units for coding information. These are called nucleotides and there are only four.

Cytosine, adenine, thymine and guanine.

The following is a list of the gene codes. They are called codons.

Ile, leu, val and asp.

The following is a list of the protein codes. They are called amino acids.

Alanine, valine, glutamine and serine.

Do you think polycistronic mRNAs are more likely to be expressed or less likely to be extrachromosomally transmitted?

I would posit that they are more likely to be expressed. There is very little harm in this sort of transmittance, since it can only occur during the embryo stage of development when any aberrant phenotypes will not have a chance to manifest due to cell death.

If the phenotype is viable, it will be expressed, and because more traits are coded for in a polycistronic mRNA than in a monocistronic one, then more of these traits will probably be expressed. Furthermore,

A polycistronic mRNA is more likely to be expressed because of the use of a single ribosome, which has an increased rate of translation when compared with one used for monocistronic mRNA.

This makes it easier to simultaneously translate the three mRNAs that are coded for. An mRNA with a single open reading frame will be subject to ribosomal pausing and nonsense-mediated decay.

However, a polycistronic mRNA is more likely to be expressed because it utilizes a single ribosome during translation. This increases the rate of expression and decreases the likelihood that any of the three mRNAs will not be translated.

It seems that the idea of polycistronic mRNA exists because cells' pre-mRNA need to be processed in such a way that they can produce the correct proteins, at the right time. However, my analysis suggests that this is not as hard a problem as it initially appears. My hypothesis is that when cells are synthesising mRNA in preparation for protein synthesis, their internal mechanisms (which can include other proteins) will naturally sort out which mRNAs go with which tRNA's and also where those molecules end up within the cell. It doesn't really require any intelligence or computational power to do so, since all it would take is a large enough number of possible combinations of mRNAs meeting up with tRNA's and then sorting them into different parts of the cell based on what each molecule should do.

If this is the case, then there is no real need for polycistronic mRNA. It's just an artefact of evolution which arose because it was a slightly easier solution than making individual mRNAs from scratch in such a way that they always ended up with their correct tRNA.

However, I do see why this is a problem for biologists. It's not really something that can be easily tested and observed which makes it more difficult to prove or disprove my hypothesis.

At the moment, my hypothesis remains unproven. However, if I ever kill a biologist then it will be proven to be true.

So, for now I will remain open minded about the existence of polycistronic mRNA.

Of course, this is a pretty big philosophical issue so I can't say that I'm too surprised if my hypothesis isn't correct and there are other mechanisms in place to ensure cells end up with the right mRNAs. After all, it's not even clear how life got started which makes me think that the explanation behind polycistronic mRNA might be just as mysterious.

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