Seemingly Random #mutation evidently can be concluded as one of the most important driving forces of #Evolution,
and consequently,
vast diversity of life on our little Blue Globe.
Just to recap from previous article.
Concept of Evolution: The Driving Forces of Evolution
There is several distinct forces behind shaping of diversity of living, and non-living orgainsms alike.
Previously we talked about Natural selection and it's kins.
In this article we are going to explore Mutation and other changes at the genome level.
Mutation, viral transmission, and genome rearrangements- Genetic drift, including Founder Effect, and Bottleneck Effect
Natural selection, and Red Queen EffectSexual selection- Gene flow, and Isolation
Mutations, what exactly are they?
In most simple terms,
mutation is a change in genetic material of an organism.
Every living and non-living organism known to mankind,
have a blueprint for it's structure encoded inside of it.
In case of biological beings,
that kind of blueprint is composed of off either RNA, like some viruses,
or DNA like everything else we ever encountered.
Whether you grow tall, or short,
thin, or wide,
gain muscle, or gain fatty tissue,
your eye colour,
skin pigmentation,
bloodtype,
and even your sex.
Nearly everything about your body that makes you You,
it's all encoded within your DNA.
DNA oftenly is referred to as a code with letters forming information.
That is of course because this kind of metaphore make it easier to understand the how it works.
In reality,
mechanisms DNA operates with within the cell are purely dependent on thermodynamical probabilities of interactions and reactions between particles in an environment of certain dynamics and concentrations.
A little more or little less "salt" in your cells, and your DNA start to operate quite differently than normal.
So yeah,
a code,
spelled with letters.
That sounds much more simple.
With this basic information on the way DNA operates,
we can finally get into mechanisms of mutations.
A DNA [or RNA] sequence is in no way fixed.
It can change very frequently.
Change in the sequence of the code is called a mutation.
Mutations can be either harmful, neutral, or other.
Most of changes in genome which can be seen, which manifest, are harmful,
vast majority of traits controled by genes in an individual
are in apparent harmony with eachother.
A minor change in one of 1000's of components may very well trigger a chain reaction
which then lead to illness, deformity, and even death.
Cancer is a very good example of a direct result of change in balance of genes due to mutation,
genes controlling cell divisions,
if disrupted,
may lead to uncontrolled proliferation of cells and in consequence tumorogenesis, tumor growth.
We all know where that may lead an individual. Death.
A point mutation can result in Change of one Letter for another,
Deletion of a Letter,
or Insertion of a Letter in a sequence.
Deletions and Insertions,
if we're dealing with a single letter change,
will result in a shift in the reading frame on the DNA sequence.
Not all mutations can be seen.
In fact,
a huge portion of mutations have no particular effect on the organism.
That is a neutral mutation.
DNA sequence codes for proteins using triplet of letters,
but changing one letter in a triplet
don't necessarily change the way cellular machinery interpret said triplet.
Hence, mutation in DNA may occur and final protein product is exactly the same as without the mutation.
There's also a possibility that, even if the final protein product have slightly different amino acid sequence itself,
the structure, and consequently the activity of that protein remain the same.
And finally, there are all other mutations.
Why other?
Why not beneficial?
Must mutation not be beneficial?
They can absolutely be.
The thing is,
like we explored in a previous article,
the environment, putting the pressure on inviduals,
it determines whether a trait is beneficial, and help in survial,
or perhaps the opposite, and results in decrease of survivability.
Let's explore an example.
Sickle-cell disease,
a genetic condition of blood in which our body,
due to mutation, produces incorrect vatiant of Heamoglobin in our red blood cells,
consequently decreasing the amount of oxygen a cell can deliver to tissues
and cells viability.
It should be seen as a negative trait,
unless
you live in an area where you may be exposed to malaria infections.
Sickle-shaped red blood cells appear to display a resistance to infection with malaria spores.
Suddenly it becomes beneficial to have this mutation.
Before we move on to viral transmissions,
let's recap key points we learned about mutation thus far.
It can be deadly,
it can be silent and insignificant,
it can be beneficial in one circumstance,
and harmful in another.
A change in one letter of DNA is called a
Point Mutation
Point Mutations can insert or delete a letter within the DNA sequence, as well as change one letter to another.
The selective pressure determines whether a non-lethal mutation is beneficial or not.
Viral Transmission.
Virus in our common understanding is usually seen as something harmful, potentially deadly.
And for good reasons.
Every year many people are infected with various strains of virus
and every year a portion of those people don't make it.
There are 1000' of viruses.
They can be as serious of a threat as HIV [AIDS], HBV [Hepatitis B], SARS, or Influenza,
they also can be as mundane as common cold related viruses, or HSV-1 [Cold Sore]
There are also those who are simply unable to infect human cells.
However, what we're supposed to focus on here, is not whether a virus can cause illness.
Some viruses have a peculiar ability build into their genetic structure.
The ability is called transpositon.
They can paste their own genes into the genome of their host,
as well as cut it out,
and occasionally
paste it again in different place.
By doing so, they disrupt gene expression of the host at random.
Sometimes it may lead to cancer.
But on rare occasion,
through copying and pasting viral genes between various hosts during the viral "life" cycle,
virus start carrying parts, or even whole genes of one host and transmit them to another.
If said fragment transmited through viral activity stabilizes within host genome
it becomes an integral part of a gene pool in a population the host belong to.
If by sheer chance it is beneficial, it's frequency within a population may increase.
Finally, we arrive at Genome Rearrangements
There are 5 important types of mutation in this catergory.
- Insertion
- Deletion
- Translocation, or Transposition
- Duplication
- Inversion
The idea is very simple.
Due to the mechanisms governing DNA, usually during it's replication, maintenance, and cell division.
One, Two, and even all of those rearrangements may occur.
Insertion of an entire segment of genome in a place it don't belong,
or Deletion of a segment resulting in lose of a portion of genetic information.
Translocation means that portion of genetic information is moved from one place in a genome to another.
Duplication implies that the number of copies of a gene, or genes increase,
and Inversion is an even in which the direcion the gene is read is reversed.
To be continued...
See also previous articles:
Concept of Evolution: The Ladder of Complexity vs The Tree of Life
Concept of Evolution: Modern Synthetic Theory of Evolution
Concept of Evolution: The Driving Forces of Evolution
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created to explain in simple terms certain scientific concepts.
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