Question being, what does this world actually entail?
The idea of “genetics” has been brought up loosely these days. A lot of people don’t even understand what they mean when they say things such as:
- “He/she looks so physically attractive. They have good genes.”
- “I’m lazy. My parents were lazy. Hence, laziness is genetic.”
- “(Insert abnormal condition here) is caused by abnormal genetics.”
- “It’s in our DNA to be (insert positive descriptor here).”
What, even, is a gene? How does our DNA fit into the equation, even?
The idea of DNA and what it represents
Our bodies comprise roughly 38 trillion cells, which differentiate into different cells to support the function of different systems in the body.
These cells possess unique identifiers known as DNA (or deoxyribonucleic acid). DNA is a molecule comprising two polynucleotide chains that is arranged in a double helix manner. The polynucleotides contain simpler nucleotide molecules that interact and bind with each other.
There are 4 main nucleotides: cytosine (C), guanine (G), adenine (A) and thymine (T). These nucleotides form either C-G or A-T base pairs, which form the structure of the double helix. It is estimated that the entire human genome contains 3 billion C-G and A-T base pairs.
The information that is contained in these base pairs provides cells with their ability to synthesise biochemicals that are important for signalling within the body, such as proteins.
A gene in the human DNA is a fragment of those base pairs that, when active, signals a cell to contains 27000 base pairs, though some can go up to be as big as 2 million base pairs.
Therefore, the 3 billion base pairs are necessary to encompass all the different genes and functions that our body needs to survive and thrive.
These genes tell the cell what proteins they ought to be synthesising:
In the genetic code, each group of three nucleotides — known as a “triplet” or “codon” — stands for a specific amino acid. For example, GCA stands for alanine, AGA stands for arginine, and AGC stands for serine. There are 64 possible codons, but only 20 amino acids, so more than one codon may code for a single amino acid. For example, GCA, GCC, and GCG all mean alanine.
Not all genes will be active in all cells, of course — we can’t expect a bone cell to behave like a liver cell, for instance.
Much like how we wouldn’t expect an accountant to be doing the work of a technician, right? Their skillsets are different.
When it is time for a cell to replicate, the information from the DNA molecule is copied as such:
When a cell needs to copy a DNA molecule, it “unzips” part of the double helix, breaking the rungs of the ladder in half so that the molecule separates down the middle. New nucleotides, floating free in the cell, can then hook up with complementary nucleotides along each strand. Gradually the unzipping proceeds, and the new strands continue to grow until one DNA molecule becomes two identical DNA molecules.
This mechanism is catalysed by the DNA polymerase enzyme, which connects free nucleotides with the existing nucleotides in each strand.
That’s what is IN our DNA, from a purely biochemical standpoint.
How do things go wrong genetically, then?
The copying mechanism can go wrong as information is transmitted from the sperm cell of the father and the egg cell of the mother to the development of the foetus in the mother.
With the billions of base pairs that are being copied, we can’t ensure that DNA polymerase will get things right all the time.
It is very much like a photocopying machine, where repeated copies of a photocopy results in the quality of the subsequent copies to be visibly diminished.
Instead of C-G or A-T coupling, we can sometimes see the formation of odd C-A or G-T pairings. We can also see possible insertions of new base pairs or deletions of original base pairs, which exacerbate the copying mechanism’s errors further.
If most base pairs are lined up and copied correctly from the DNA of both parents while synthesising the DNA of their child, the child should not be born with visible health problems.
However, encoding errors can result in birth defects or the child being born with “genetic” disorders — things that cannot be cured because the child was borne out of a defective DNA copying mechanism.
For example, cleft palates in children can be attributed to errors in DNA synthesis and replication.
Hence, some people can be born with cleft palates. As multiple genes contribute to the risk of developing autoimmune diseases, it also isn’t surprising to see children born with issues such as Type 1 diabetes either.
It’s all a matter of faulty DNA replication.
It’s not even the fault of the parents. They may be the healthiest and fittest men and women on the planet, but even that does not reduce the probability of their children being born with no defects down to ZERO.
Another way would be the misrepresentation of codons. If we have 64 different codons that encode 20 amino acids, the erroneous insertions or deletions can contribute to an encoding of malfunctioning proteins.
As most of these proteins require specific configurations and structures to be at their most efficient performance levels, an erroneous encoding could lead to the development of a faulty “lock” in the protein that either refuses to work with the correct key, or works with the wrong key, which isn’t good for the body either way.
Having a defective gene that we’re born with will also result in problems with our cellular functions.
For example, some people have a defective methylenetetrahydrofolate reductase (MTHFR) gene, which results in the body’s inability to regulate homocysteine levels when the defective MTHFR genes are not producing enough MTHFR to deal with the homocysteine. This is considered to be important because homocysteine:
was also found to stimulate IL-1β production by human peripheral blood monocytes and TNF-α production by monocyte-derived macrophages.
Even if we aren’t born with it, we may still develop it later on (lifestyle choices).
Our cells are constantly reproducing and forming new cells. Each replication cycle brings on a new probability of copying errors.
It is up to the immune system to eliminate defective cells via autophagy (phagocytosis). Digest them up, so that their nucleic acid material can be recycled and repurposed to synthesise the next cell (hopefully with less major defects).
However, if one’s autophagy mechanism is dysregulated, then the clearance of these affected cells will proceed more slowly, resulting in an accumulation of cells with oxidised DNA in the body.
Do our genes predispose us to be more susceptible to chronic inflammatory diseases, then?
The human genome contains so many different genes, as I have mentioned earlier. What do we mean when a disease is “genetic”?
It means that the genes in a cell line aren’t pulling their full weight. They aren’t producing the specific proteins that the body needs to function properly in a sufficient manner.
Have you ever missed the cut by a fraction of an inch before?
Scoring 49 points out of a 100 point exam, for instance.
Stretching to reach an object but just falling short of reaching it.
That’s what it’s like when the cells aren’t producing enough of those proteins.
It could be a gene production/transcription issue — but hang on a minute, why is it only appearing now when it ought to have appeared before that?
As it is in the case of high cholesterol, for instance — why is it that the issue only appears so much later on in life for most people?
Is it something to do with protein production, or could it be that the proteins are being produced normally, just that they end up getting destroyed or deactivated more readily for some other reason?
Of course, it could also be an epigenetic problem, where lifestyle or environment issues change up gene function radically over a long period of time.
But it’s not fair to say that most diseases are “genetic”, that’s what I’m driving at.
It’s very easy to misuse that word when we want to sound smart (or when doctors would like to avoid a long explanation), but I don’t really think it’s fair to say that certain diseases are “genetic”, especially if one doesn’t even understand the process behind how all the biochemistry goes wrong in the body!