Are we our bodies or our minds?

Human beings are some of the most complex organisms on the planet, not just in terms of pure biochemistry, but in the way we have cognitive thought processes, feel emotions, and perceive the world around us. We have a constant internal narration and multiple conscious and unconscious thoughts all the time, and our bodies help us to experience and explore our surroundings. But where is the line between physical being and conscious thoughts that defines who we are? Ignoring the ethical concerns attached to the idea of a brain transplant, I wonder what would happen to a person if they received a new brain – who would they be?

When initially looking at the structure and function of the brain, I believed there would be a few key areas that make all individuals unique in terms of who they are: the parietal lobe (in the cerebrum) the hippocampus, the cerebellum and the limbic system (under the cerebrum).[1] The parietal lobe is important for interpreting words, sensing touch, sound and pain, interpreting sensory stimuli, and spatial awareness – this is a part of the brain that helps determine how, as individuals, perceive the world around us. The hippocampus is where long term memories are ‘stored’ and the limbic system is the area where emotions stem from.

However, there appear to be lots of areas that interpret sensory stimuli, and although the hippocampus is the main area associated with memory, there are other areas that do this as well. Interpretation of language occurs in the temporal lobe too, not just the parietal lobe. It is easy to see that the brain is intricate and complex, and within the gross structure it is difficult to isolate parts that determine who we are – I suppose it depends how you classify people. Some would argue that the cerebral cortex, where logical thinking comes from, while others would argue that the limbic system, as a source of emotions, is where the real inner self arises from.

Hypothetically, if a person was to have a brain transplant I would say that the original “owner” of the transplanted brain is the person that would still be alive following the procedure, just in the body of someone else. If all the nervous connections were remade, then I imagine then that brain would perceive the world from a new body with altered senses, given their new sensory connections. All the information such as memories would be stored in the brain and so the person leaving the operation would have memories from living in a whole different body… spooky! It is also worth noting that the muscle memory and co-ordinated control of gross motor skills and posture (as controlled by the cerebellum) would all be in-tune for the previous body, so the new person could be clumsy following the operation as the brain registers the new relative positions of their limbs.

There are so many things to consider before even looking at the ethical issues with regards to brain transplant. I think it is a very interesting thought experiment to work out which person – the brain or the body – would really come out of the operation.

[1] http://www.mayfieldclinic.com/PE-AnatBrain.htm

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Significance of the Peak/End Rule

A lot of how people perceive the world around them is as much to do with psychology and what goes on in your head, as what actually happens according to objective measurements. Would you prefer one moment of intense happiness, or being a little bit happy for an extended period of time?

There are many studies which have been done, using various different trails, in which people are subjected to pain (or pleasure) for different lengths of time and at different intensities, according to a person’s individual pain threshold. The best predictor of how someone would afterwards rate the experience, was not in fact the length of time which they spent experiencing any given amount of pain, but the peak rating, an the end rating. This is known as the Peak End rule.

Looking at study [1], subjects placed their hands in cold water for 60s, and then repeated this for 90s, but with the water temperature increased by a degree on the last 30s. To an objective observer, it seems clear that when faced with a choice of the two, one would opt for the first: less time in pain. However, of the participants in the trial, “A significant majority chose to repeat the long trial, apparently preferring more pain over less”[1]. This may seem bizarre, so if we look at another experiment, do the results follow the same trend?

It is very curious when looking at the different between what is perceived at the time, versus what is remembered afterwards. This (not unrelated) concept was put to the test during operations [2], where patients were kept awake and asked to rate their pain at regular intervals, on a scale of 1-10. After the procedure had finished, patients were once again asked to rate their experience. The best correlation between the retrospective opinion of the procedure and the data obtained during the operation was most accurately predicted by the peak pain felt at any one time (an extreme point in the emotional memory) and at the end of the procedure – or the lasting impression. The duration of pain was almost irrelevant when the ‘remembering self’ came to look back on the experience.

This is important to remember when making decisions about experiences. The remembering self does not hold an accurate picture of what actually happens, therefore cannot necessarily be relied upon when passing judgement on previous experiences. In a many circumstances, the clinical setting included, it may be possible to bias a person’s memory of an experience, such that they may be more willing to undergo a painful experience again, due to their remembered perception that it was not all that bad. As to how long the peak end rule extends, I am not aware as to whether this has been tested. For example, could a week-long holiday be ruined in retrospect by a horrible experience going through the airport to come home? Or is the airport experience filed somewhere different, leaving a good memory of the holiday, but not of airports. This is for future studies to determine.

[1] http://journals.sagepub.com/doi/abs/10.1111/j.1467-9280.1993.tb00589.x

[2] http://www.sciencedirect.com/science/article/pii/0304395996029946

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The Holistic Approach

How often do we look for a quick fix to isolated problems? I don’t know if this is a culture related, or based on the modern lifestyle of our day and age, but I think that we need to change the way we deal with certain problems; with a slightly different perspective could improve patient doctor relationships, acute problems and chronic health.

Looking at ‘the elderly’ (this is a broad generalisation) gives a clear example of the issue I would like to address. People of the older generation tend to have many health problems – or more than one, at least. If an elderly person came to the doctors with a chest infection, there is an acute problem that can be dealt with. Except for the fact that this patient suffers from high blood pressure, so takes Warfarin to thin their blood and prevent clots; the combination of amoxicillin and Warfarin could lead to over-anticoagulation, due to effects of the antibiotic that inhibit platelet aggregation (clotting). The go-to antibiotics that may ordinarily be used to treat the chest infection are suddenly compromised by their interaction with another drug that the patient is already on – which drug is stopped? Is there an alternative drug that could be used to achieve the same effect with out the same risks and side effects?

For all people, young and old, the interactions between the drugs that they are being prescribed is an obvious point for the doctor to check; processes in the body rarely take place in isolation, so it is almost unnatural to treat illnesses as singular obstacles. But the holistic approach extends far beyond the immediate needs of the patient with regards to their drugs. This includes accounting for the psychological effects of  recent amputation, or educating a newly diagnosed celiac sufferer how to prepare meals for them-self, gluten free.

For some doctors (and patients) this may be a newsflash, but the role of the doctor is not to diagnose, prescribe, repeat. Yes, there are other healthcare professionals who are trained to look after the patient’s'everyday needs’ but actually if we want patients to be healthy and look after themselves as best they can, we need to educate them on how to do so. This includes simple instructions such as, “after this operation, do not walk on this leg for 24 hours, then only light duties and necessary movements for the following week. Moisturise the skin regularly while the stitches are in, and the scar will heal neatly”. This could make the difference between recurring problems and multiple follow-up visits to deal with repercussions of too much high impact activity on a healing wound for a patient who received no advice and thought they could just get on with life from the day after the op, and the patient who rests, recovering with nothing more than a tiny scar as evidence.

Seeing people as individuals, not as the problems they present with, is paramount to a holistic approach in medicine. A patient does not stop being the patient when they leave the doctors consultation, any more than they stop being a person, therefore the care and advice that a doctor provides should sustain the patient once they have left. When health issues arise, these are not additional problems to be solved, but an added complication to the case in progress, and should be dealt with as such: in light of the current situation of the patient.

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Controlling Water Losses

A few months ago, I posted about the bladder, wondering how water is compartmentalised inside the body. I have since found out more information, and thought that this was a good topic to revisit now that I have a wider understanding, although I am still nowhere near expert!

The key to understanding water balance begins before the bladder, in the kidneys where blood is filtered and a constantly adjusted volume of water is reabsorbed according to the body’s needs. Blood enters the kidneys through the renal arteries and passes along arterioles to nephrons, where high pressure in the glomeruli forces tissue fluid (plasma and the substances dissolved in it) out into the Bowman’s capsule - this is ultrafiltration. In the proximal convoluted tubule (the first coiled tube that the filtrate passes through) most of the useful substances, like amino acids, glucose, mineral ions, are reabsorbed, leaving behind mainly nitrogenous waste (urea) and water. The filtrate then travels down the Image result for loop of henle diagramLoop of Henle. In the upward branch, ions are actively transported out of the tubule, but the walls are impermeable to water, so water cannot leave. This lowers the water potential of the surrounding tissue fluid in the medulla of the kidney, and draws out water from the filtrate in the descending limb, by osmosis. This process allows most of the water that was removed from the blood initially, to be replaced: water in the medulla has a steep gradient maintained as water moves into the peritubular capillaries and is taken away. The difference in water potential is very important because it is this gradient that determines the concentration of urine.

When fluid leaves the loop of Henle, it enters the distal convoluted tubule, another coiled section of the nephron, and has a higher water potential than the surrounding fluid: at the top of the ascending limb, ions were pumped out but water could not leave. Water can move out of the distal convoluted tubule by osmosis, at a rate which is controlled by the antidiuretic hormone (ADH). The distal convoluted tubule has walls made up of cells with ADH receptors – when the body needs to conserve water (for example when you don’t drink enough and start to become dehydrated) ADH is released and binds to cells in the walls of the distal convoluted tubule and collecting ducts. In this case, the walls become more permeable to water, and as the fluid passes along the tubules through the medulla (region of very low water potential) water easily leaves the filtrate by osmosis, resulting in the ability to produce urine more concentrated than an organism’s own blood: hypertonic.

Once this urine has been produced, it flows to the pelvis of the kidney, drains through the ureter, and moves to the bladder where it is stored until such a time is convenient for excretion. Within the bladder, the inner layer is called a mucosa, in the same way as many other internal organs, but the mucosa in the bladder is specialised to protect the muscles in the walls, from the urine that it stores, and  the waste products it contains. The bladder mucosa is not very permeable to water, so urine can be stored at lower water potential then the blood,without drawing water away from tissue fluid surrounding nearby cells by osmosis.

 

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How Specific is Body Chemistry?

Chemically there are many different monomers, macromolecules and ions that play hugely varied roles in our genetic, chemical and physical make up. But just now specific do we need to be?

In some cases, the human body (and many other organisms) is frighteningly specialised: cells have only certain genes switched on, so that they can only produce particular proteins. Enzymes can only catalyse* one reaction, where the substrate particle is a precise complementary shape to that of the enzyme. DNA base pairing is so exact that each base in a sequence of DNA can only fit with one other partner. Antibodies fit antigens in an absolute manner; hormones can only bind to specific receptors on/in cells; the body will exclusively use L amino acids, where a chiral carbon is involved**… The body seems to be very high maintenance when it come to fitting things together exactly right!

However, the DNA is a degenerate code, whereby there are more combinations of base pairs in the triplet code than there are amino acids to code for – some alterations to DNA have no effect on protein structure because the same amino acid has been coded for by a slightly different triplet code. For example, both TTA and TTG code for the amino acid leucine. So in some circumstances, DNA can change with little apparent consequence.

How about if a different amino acid was used to make an essential protein? In most cases, this would result in the protein containing a different balance of charged R groups, so wuld become a different shape, and almost certainly be dysfunctional. However, if Arginine was replaced by Lysine, the effect may not be significantly noticeable as both have positively charged NH3+ groups. The overall charge (the main factor determining tertiary protein structure) has not changed, so the protein may in fact have the same shape. It appears that even swapping one amino acid for another does not always lead to a disaster.

So what if a very important enzyme, such as catalase, had a whole bunch of amino acids changed? Again, in most cases changing a large section of a protein’s primary structure would be catastrophic, but similarly if the active site of the enzyme was unaffected by this change, then it doesn’t matter what the shape of the rest of the molecule is! How bizarre is that? Often the shape of the rest of the protein helps determine the shape of the active site, but there are many essential enzymes that show variation in chemical make-up between individuals, despite the fact that we all have the same enzyme.

From an evolutionary perspective, the things that work are conserved – it appears that some things have to be precisely specific in order for them to work, whereas there is some leeway in the composition of other parts of our bodies. Its good to know that we are not exact jigsaws, but that the body can take a slight mistake in its stride, and changes on the molecular level, whilst some are devastating, others can potentially go unnoticed.

*the forwards and reverse of

**Chiral carbons have 4 different chains branching off of them, such that a mirror image of the molecule is not superimposable onto the original, and therefore the two molecular arrangements of the same structure, are in fact chemically different. In biological systems, the L version of all stereo isomeric amino acids is used in preference to the D version, and so enzymes only fit the L amino acid, to fit together and make into proteins. The D versions are not recognised, as they do not fit into an enzyme’s active site in the same way, so cannot be used. There are important implications of there being two versions of certain (chemically otherwise identical) molecules, such that the L version fits into desired receptors, while the D version does not, and in fact causes a completely different series of side effects as it fits somewhere else.

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The Alcohlic Liver

The liver is the single largest internal organ in the human body, and carries out many different complex and chemical functions. The liver is responsible for: storing glycogen/releasing glucose to change blood sugar levels; secretion of bile and production of bile salts, which enter the small intestine and emulsify fats to help break them down; removing toxins and waste products from the blood supply before it goes to the rest of the body; breaking down excess amino acids that are not made into proteins; removing and breaking down hormones in the bloodstream.[1] This list is not extensive, but includes some of the major and most important functions of the liver.

Given that the liver does so many different things, why is it that alcohol has a particularly bad effect on it? The liver breaks down toxins delivered to it, which includes alcohol. When a person consumes alcohol, the body is provided with a chemical that is not useful as a substrate for any particular metabolic pathway, so needs to be broken down and excreted. Many of the breakdown products are more dangerous than the alcohol itself, such as acetaldehyde, which is “a highly reactive and toxic molecule that may play a crucial role in alcohol-related liver damage”[2]. Acetaldehyde can be a problem to liver cells on an individual basis, altering cell function and gene expression so that they do not function correctly, or produce necessary proteins. This chemical can also alter the structure (and therefore function) of proteins produced.[3]

The damage done to the liver is almost directly correlated to the volume and frequency of alcohol consumption – the liver is a versatile organ that regenerates quickly, but frequent ingestion of alcohol means that it is working very hard to break it down, with little time to recover and regenerate. Of course, the more alcohol that passes through, the more there is to break down, releasing larger quantities of harmful acetaldehyde to wreak havoc.

A major problem that can result from regular, long term, alcohol consumption is cirrhosis: damaged liver cells are replaced by scar tissue, due to chronic inflammation[4] or swelling.* The scar tissue does not contain the right cells to perform normal liver function, so compromising the organ’s ability to carry out all the processes that it would usually do. the passage of blood, tissue fluid and other substances into the organ and between the cells, leading to cells (both damaged and healthy) becoming malnourished; the liver tissue can become lumpy and hard, and pretty much dysfunctional.

[1] Burnie, D. (1995). Concise Encyclopaedia Human Body. London: Dorling Kindersley Limited, 122-123.

[2] https://pubs.niaaa.nih.gov/publications/arh27-4/285-290.htm

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952076/

[4] http://loveyourliver.com.au/alcohol/

*Cirrhosis can develop as a result of or in addition to other (alcohol related) liver problems, such as fatty liver or Hepatitis C.

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Problems of a Multicellular Organism

One of the difficulties faced by people is not diseases caused by invading micro-organisms, but issues where the body itself is incorrectly built or programmed, and so not everything functions as it should. These problems can be from birth, or they can develop for no apparent reason as an individual gets older, often due to small changes in the internal environment. One example of complications caused by a tiny part of the body not quite working as it should, is Barrett’s oesophagus, often caused by long-term issues with reflux from the stomach.

When we eat, food leaves our mouth at the back of the throat and travels down the oesophagus into the stomach, an organ specially designed to produce and hold hydrochloric acid (HCl) at a highly acidic pH of around 1.5-3.5. This environment is not compatible with other cells, even those nearby in the base of the oesophagus; these oesophageal cells are usually protected by a sphincter at the gastroesophageal junction. During normal digestion, the sphincter, a ring of muscles, relaxes and opens to allow food to pass into the stomach, then contracts and prevents food from re-entering the oesophagus. On occasions of reflux (for example, when burping) the sphincter will relax to allow substances out of the stomach and back into the oesophagus. This is a normal, healthy and co-ordinated function.

However, if the sphincter is weak, or presents inappropriate periods of relaxation,  individuals can suffer with reflux on a regular and/or long term basis, which often causes other problems to arise. When stomach acid, pancreatic juice, bile or other chemicals present in the stomach, are allowed into the oesophagus this can cause complications for the oesophageal cells, and result in swelling at the base of the oesophagus. If this occurs frequently over long periods of time, the cells have little chance to recover, so reflux can lead to Barrett’s oesophagus. The squamous and ciliated epithelial cells that form the lining can have genes switched on (which are usually off) as a result of chemicals from the stomach which they would not normally be exposed to. In some cases, it has been found that bile can trigger metaplasia (significant abnormal change in the nature of a tissue) and cause these lining cells to differentiate into intestinal cells.[3] Clearly this is bad: intestinal cells secrete all sorts of enzymes and proteins that could be very detrimental to epithelial cells further up the oesophagus, but would not actually damage those cells which already behave a though they are intestines.*

Frequent, chronic heartburn (a burning feeling that arises from the abdomen up towards the neck [1]) is the main warning symptom of Barrett’s oesophagus beginning to present. The development of Barrett’s oesophagus can be slowed or even prevented by “medications to control acid production or secretion (primarily proton pump inhibitors). Proton pump inhibitors (PPIs) are recognized as the most powerful and effective drugs used to inhibit acid secretion and allow healing of tissue damage in the esophagus”[2]. However once metaplasia has occurred it is an unknown feat to change the cells back – an operation to remove the tissue is likely to be necessary.

[1] http://patient.info/health/barretts-oesophagus-leaflet

[2] http://www.aboutgerd.org/what-is-gerd/barrett-s-esophagus.html

[3] http://www.surgery.usc.edu/foregut/demeesterpub/286.pdf

*The changing of cells and rapid growth of new cells can develop into cancer. It is worth noting cancer is a rare but possible outcome.

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Moles in the Skin

The skin is made up of many layers, the outermost of which is the epidermis. This includes keratinocytes, which make up the majority of the outermost layers – these cells grow outwards continuously to replace those that die and flake off. In the basal layer of the epidermis are melanocytes[1], which are the cells responsible for producing pigment and colouring the skin and other parts of the body, such as the eyes. In the skin, melanocytes produce the pigment melanin and package it into vesicles (melanosomes)  that are transferred from the melanocytes to the keratinocytes.

The purpose of melanin is to protect active or living skin cells (and consequently other boy cells deeper in the body) from being damaged by sunlight or other forms of radiation. The pigment molecules are designed to absorb radiation. When skin is exposed to sunlight, the amount of melanin produced varies, depending on genetics and sunlight exposure. As exposure to radiation increases, the body’s reaction is to produce more melanin – hence people get tanned when their skin sees more sun than usual, but this tan fades gradually to normal when the level of exposure drops.

Although there are different types of moles, which can be caused by different things, many are simply a result of melanocytes, which are usually spread fairly evenly across the skin, growing in clumps. More melanosomes are produced in a concentrated area, and so the keratinocytes in these spots contain more melanin than other cells nearby. This is why, although the top layer of skin cells comes off, freckles or moles remain – the colour is not produced in the cells that flake away, but in those found in a slightly deeper layer of the skin.

Moles in themselves are not dangerous, and can appear after exposure to high levels of radiation, as a result of the increased number of melanocytes and melanin produced. However, if you notice anything unusual about an existing mole, or the sudden appearance of e new mole, it is worth keeping an eye on and being aware of. Whilst moles are as harmless as the skin itself, some can develop into a melanoma. “Melanomas usually appear as a dark, fast-growing spot where there was not one before, or a pre-existing mole that changes size, shape or colour and bleeds, itches or reddens.”[2] If a mole begins to present with any of these symptoms, that is changing shape, growing visibly or rapidly, or becoming itchy, it may be worth getting checked by a doctor.

[1] http://www.dermnetnz.org/topics/the-structure-of-normal-skin/#A

[2] http://www.nhs.uk/conditions/moles/Pages/Introduction.aspx

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Chronic Fatigue Syndrome (MS)

I read this today and thought I would share – this is not my opinion or even experience, but I have a friend with CFS and this explains some of the things which she finds difficult to talk about. A very interesting read…….

Hi my name is Myalgic Encephalomyelitis… some friends who have known me for a very long time call me M.E …… I’m an invisible inflammatory disease that attacks your sympathetic nervous system.
I am now velcroed to you for life. If you have M.E you hope for remission but there is no cure.
I’m so sneaky–I don’t show up in your blood work, in x-rays, MRI’s can’t detect me, basically there is no test to prove you have me. There are only test to rule out other things.
Others around you can’t see me or hear me, but YOUR body feels me.
I can attack you anywhere and anyway I please. And, I will. Constantly.
I can cause severe pain or, if I’m in a good mood, I can just cause you to ache all over.
Remember when you and energy ran around together and had fun?
I took energy from you, and gave you exhaustion. Try to have fun now.
I can take good sleep from you and in its place, give you brain fog and lack of concentration.
I can make you want to sleep 24/7, and I can also cause insomnia.
I can make you tremble internally or make you feel cold or hot when everyone else feels normal.
I can cause one limb to change color, look bruised, feel super sensitive randomly for seemingly no reason.
I can also give you swollen hands and feet, swollen face and eyelids, swollen everything.
OH, and just because I started off in one part of your body, don’t think I can’t travel and effect other parts of your body I so choose to torment. I can, and likely I will.
I can make you feel very anxious with panic attacks or very depressed. I can also cause other mental health problems. You know crazy mood swings? That’s me. Crying for no reason? Angry for no reason? That’s probably me too. It is hard to not feel hopeless when you have me beating your body up constantly.
I can make you scream out loud, anytime of day or night, anywhere you are because I can create pain that makes you sure someone just stabbed you with a knife. Making you look crazy is fun for me.
I can make your hair fall out, your nails become dry and brittle, cause acne, cause dry skin, the sky’s the limit with me.
I can make you gain weight and no matter what you eat or how much you exercise, I can keep that weight on you. I can also make you lose weight. I don’t discriminate.
I hear you’re going to see a doctor to try and get rid of me. That makes me laugh. Just try. You will have to go to many, many doctors until you find one who can even try to help you effectively. Most of them will make you feel like you are to blame, or worse, it is all in your head. I’ll convince them that you are crazy because normal people know that you can’t have all those symptoms all over your body and still walk around looking normal.
You can be put on the wrong medication, pain pills, sleeping pills, energy pills, told you are suffering from anxiety or depression, given anti-anxiety pills and antidepressants.
There are so many other ways I can make you sick and miserable, the list is endless – If your body is all of a sudden dealing with things that were never issues before…yep…. that’s probably me.
Shortness of breath or “air hunger?” Yep, probably me.
Bone density problems?
Can’t regulate body temp and poor circulation?
I told you the list was endless.
You may get massaged, told if you just sleep and exercise properly I will go away.
You’ll be told to think positively, you’ll be poked, prodded, and MOST OF ALL, not taken seriously when you try to explain to the endless number of doctors you’ve seen, just how debilitating I am and how ill and exhausted you really feel. In all probability you will get a referral from these ‘understanding’ (clueless) doctors, to see a psychiatrist.
I will make you question your own sanity at times.
Your family, friends and co-workers will all listen to you until they just get tired of hearing about how I make you feel, and just how debilitating I can be.
Even after explaining to those you interact with regularly that I’m the most painful disease known to man, and there is no cure, they will say things like “I hope you have a speedy recovery”. Those who don’t know me well have no idea how cruel and unusual my punishment can be.
They’ll also say things like, “if you just get up and move, get outside and do things, you’ll feel better.” They won’t understand that I take away the ‘gas’ that powers your body and mind to ENABLE you to do those things.
Some will start talking behind your back, they’ll call you a hypochondriac, while you slowly feel that you are losing your dignity trying to make them understand, especially if you are in the middle of a conversation with a “normal” person, and can’t remember what you were going to say next. You’ll be told things like, “Oh, my sister had that, and she’s fine on her medication” when you desperately want to explain that I don’t impose myself upon everyone in the exact same way, and just because that sister is fine on the medication SHE’S taking, doesn’t mean it will work for you.
They will not understand that having this disease impacts your body from the top of your head to the tip of your toes, and that every cell and every body system and organ can be effected.
The only place you will get the kind of support and understanding in dealing with me is with other people that have me. They are really the only ones who can understand.”

I think it is such a shame that people with CFS feel like they can’t talk to anyone who understands what they are going through. Hopefully this will raise some awareness and there may be a better understanding of the disease within the general public.

 

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What is the point of junk DNA?

Very simply, not all DNA codes for proteins. There are regions of the polynucleotide that code for proteins (these are exons, and make up genes) and there are also sections that do not code for anything. This makes complete sense: not all cells need to be able to produce every protein that the organism’s DNA can code for. DNA is a very clever piece of kit, because it can control what parts of itself are available in specific cells, in order that they specialise in the correct way and make the right proteins.

Every cell ion an organism contains the same DNA, all the instructions to make cells and proteins that build an organism. In eukaryotic organisms, where DNA is associated with a histone protein, the simplest way in which genes can become ‘switched off’ is by  adding methyl groups, which make the DNA macromolecule aggregate to itself, coiling more tightly around the histone protein. Therefore there is no space for enzymes or bases to begin the process of protein synthesis – there is no way of copying this DNA. Other parts of genes may be transcribed, but protein production is stopped in another way, for example the mRNA will not reach a ribosome so cannot be translated.

What is the purpose of having junk DNA in cells, which does not code for anything? Although we don’t know for sure, there is likely to be a reason because junk DNA is well conserved – this indicates that its presence may be linked to an advantageous trait, or may minimise the effects of a disadvantageous characteristic. It is likely that some sections of junk DNA have important regulatory functions, in terms of controlling which other genes are switched on or off.

One of the important reasons why we may have this junk DNA could relate to the fact that a certain length of DNA is required to keep chromosomes a comparable size which is compatible with other members of the species. If by losing the junk DNA, chromosomes became altered, this could have significant effects – or it could have no effect at all. I would like to investigate how the body knows that junk DNA is present, and yet not to code from it – would an organism still function in the absence of its junk DNA? What would be affected by removing it?

These kinds of studies would be difficult to carry out, both from an ethical and practical perspective. To be certain that a particular section of DNA is non-coding is one thing, but then to accurately remove only this section may prove very challenging. Beginning with simple, single celled organisms would be the best way to begin, as the genetic code of only one cell is altered. Any change in proteins made would be easiest to monitor in a simple organism, but behavioural changes may not be distinguishable. It may not be possible to predict the outcome of removing junk DNA until we know what it does, which begins a circular argument. (There are likely to be other ways of investigating this.)

One thing to bear in mind is that organisms are not necessarily made in the most effective way, they are just evolutionary improvements on the last system. It could be that junk DNA has no purpose at all, but is simply there because it is passed on to offspring by surviving parent organisms. It is more likely to serve a purpose, but there is a chance that junk DNA is present purely because we haven’t evolved as far as getting rid of it.

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