DNA: Four Letters

Since my mid-teens I have been fascinated by genetics. There are a numbers of reasons for this. When I was seventeen the human genome project was completed. The worlds media was abuzz with science and pseudoscience. On a more personal level I have a genetic condition called Retinitis Pigmentosa(RP) caused my a single nucleotide mutation on my X-Chromosome.

Some Science

Almost every cell of your body contains your DNA. A complete blueprint of how you are built. Its popularly presented as a colourful winding ladder. Each rung on that ladder represents a Nucleotide Base Pair. This means two nucleotides are joined together. Each complete set of your DNA contains three billion nucleotides, that’s 1,500,000,000 rungs on that ladder. There are four types of nucleotide represented by four letters – T, A, C and G. T will only bind with A and C will only bind with G. So by looking at one half of your DNA you can infer the other half relatively reliably. Lengths of those base pairs are grouped together in what we call Genes. Genes tell a cell how to produce proteins which express different traits; skin colour, eye colour, various medical predispositions, etc. A genes are then grouped together into what we call Chromosomes half of these come from your mother and half from your father, with a bit of shuffling. The last chromosome pair are your sex chromosomes which are inherited in tact from your parents with no shuffling. I’ll get into why this specifically is so cool in a bit.

Side Note: This is an extremely simplified explanation where I haven’t gone into transcription and translation or the fifth nucleotide. I’ve tried to keep it simple as I recognise not everyone has the same patient for unnecessary detail in this as me.

Mutations occur in every generation where a gene its copied incorrectly. Mutations can either be deletions where a nucleotide isn’t copied across at all or substitutions where for example a T might be swapped for a G. This may sound a bit scary but mutations are necessary for life and evolution. These seemingly accidental changes in gene expression result in new traits which, if providing an advantage will result in increased procreation and the trait will become dominant in a species.

Some History

A great example of this is skin colour. Darker skin is a survival requirement for our stone age ancestors inhabiting equatorial regions. The darker skin allowed just the right amount of melanin to be produced whilst protecting the body from the extremes of UV radiation. However as early modern humans migrated north to where the sun was far less intense they would have found that obtaining enough vitamin D from sunlight exposure was difficult, resulting in what is likely to be more disease amongst those with darker skins, slowly as mutations occurred for lighter skin these became dominant as they offered a strong advantage in the higher latitudes.

The ability to test ancient remains for genetic traits has proven fascinating. Its extremely likely Cheddar Man and all those early modern humans who came before him had “very dark” or “black” skin. This didn’t prevent him procreating as recent testing has shown 10% of the population of Britain today can probably trace their ancestry back to Cheddar Man. Whilst this 10% sadly does not include myself it does include my wife who is roughly as Caucasian as it is possible to be.

Side Note: It is a source of great sadness to me that my wife isn’t nearly as excited about her likely genetic link to Cheddar Man as I am.

My Genes – Geography

As you can probably guess I submitted my self for genetic analysis by a leading company in the field. I am really impressed with them and would happily recommend the company to anyone who wants to either leave a comment below or submit a contact form.

Before I get into the details of my report I will look back to Retinitis Pigmentosa. In my case it is the result of a single nucleotide deletion in a gene on my X-Chromosome. One nucleotide in three billion was deleted at some point in my families genetic past and it has resulted in deteriorating vision to blindness, prior to that poor colour vision, no peripheral vision and night blindness. Whilst in all likelihood I am missing a lot more nucleotides a lot of them have either been compensated for by the process of mixing my parents genes or the mutations occurred in areas that don’t appear to code for anything. This is the astounding power of these incredible little molecules.

So my genetic reports include ancestry percentages –
59.6% British and Irish,
35.7% French and German,
2.9% Other Western European,
1.1% Western Asian and North African,
0.4% Cypriot.
0.3% Other.

The company that process my genome use an algorithm that compare it to all of the other users. These databases tend to be proprietary so if I were to submit my sample to another company I may get slightly different results. They look for single nucleotide polymorphisms, which are mutations that occur and are prevalent in specific geographical areas. I would imagine globalisation complicates this process as people move around a lot more today. So these results are more about probabilities. Using this with the family tree I have put together through physical genealogical research I can say this report appears to be very accurate. The results get more detailed and show almost 45% of my genome is recently common in Cornwall, which isn’t surprising as my paternal lineage is Cornish with no real deviation or movement.

So the ancestry demographic report is, as far as I can prove completely accurate. What else did this company tell me about my genetic profile?

My Genes – Prehistoric DNA

Thanks to extraction of DNA from a growing number of prehistoric finds, particularly well preserved remains of Neanderthals we can see around seven thousand segments of DNA (not necessarily whole genes) which have been inherited by modern humans from Neanderthals. Of this possible seven thousand I have 261 which is roughly average for a caucasian British male today. I’m going to go into what this tells us about the relationship between Anatomically Modern Humans(AMH) and Neanderthals in another post.

According to my report the areas of DNA that show my Neanderthal ancestry predispose me to –
1. Prefer salty foods to sweet foods – True,
2. Have an apple body shape rather than a pear – True,
3. Be a better sprinter than long distance runner – True,
4. Prefer dark chocolate to milk chocolate – True,
5. Have detached earlobes – False.

All in all given the genes tested are only indicators or predispositions this is all fairly accurate too. The Neanderthal genome was only mapped in 2010 and there are still a huge number of ongoing projects to determine how this extinct cousin has impacted our lives.

Side Note: As previously noted I come from Cornish stock so the fact my ancestors mated with their cousins isn’t a surprise. Also I have no idea what chemical in dark chocolate is preferable to Neanderthals.

Who am I?

The reports go into a huge amount more detail however it begs the question why do I, like so many people find this so interesting?

Humans innately seek connection, our relationships kept us safe even before we were a distinct species, it allowed us to protect ourselves, to hunt and to travel. Because of this its not at all surprising we look to the past as readily as we look to the present and future to find our connections.

When answering the question Who am I? the answer is – I am a husband, a father, a nurse, a blogger, and at times a bit of a dick. My software is who I am, software coded through millions of experiences and thoughts and feelings.
My DNA gives you some idea of the specifications of my hardware out of the box, my hardware now can only be explained clinically with numbers and observation.

This doesn’t diminish the value of looking to our past but its important to put that information in the right context and use it to answer the right question.