Biology in Action
On 16th November, Year 12 students attended the event Biology in Action, students heard a number of Biologists at the cutting edge of their specialisms as well as a sessions on how to improve their Biology A-Level delivered by Examiners.
Biology in Action – Why DNA is not Your Destiny
Before Nessa began, I knew what her lecture would be regarding in all simplicity; by that point I knew that epigenetics entailed the communication between the environment and genes, but what solely intrigued me was that it had soon become apparent that epigenetics –a fairly new and developing concept and a branch of the broad topic of genetics- caused certain phenotypes and such, that simple base pairs where apparently unable to do. The speaker spoke about the epigenetic phenomena, the concept being that DNA is a script not a template. Primarily, she told us about two mice, who, although being genetically identical and put in the same environment, had variations, such as body weight. This sums up the reality of genetics, the mice’s characteristics must have been modified by an additional process instead of just a faulty genetic sequence. This was given a name: intangible variation. It is surprising to think that an organism with the same DNA; an example being a maggot and an adult fly, are so divergent, after the metamorphosis stage. We also know that epigenetics is controlled by the environment. Before the concept of Darwinism was ever gauged, we had Le Marks hypothesis, that instead of natural selection, species acquired characteristics. Although, this is commonly seen as a heresy, we can say that there are times where this concept is actually correct. An experiment was done where a mouse was constantly tormented with electric shock, after being presented with a cherry blossom, which it would promptly smell. Moreover, it seemed as if the mouse had transmitted his trauma on to his offspring, although that is still up to debate.
On the other hand, other anomalies were referenced- Nessa now explained that some species use parthenogenesis- a certain form of asexual reproduction. But the real question was why mammals are unable to do the same feat. It is common knowledge that for fertilisation to occur, there must be a gamete from the mother and the father. Using mice and the nuclei removal, an answer was formulated. The scientists were unable to get gametes from the same genders to develop efficiently, the answer simply, being because there are no differences genetically, but rather epigenetically with mammals to other species. Let’s look closer at this. The term epigenetics can be defined as additions to changes in the genetic sequence. So what really intrigued me was finding actual information entailing human defects, that had origination from such a small mechanical inaccuracy. The speaker gave two examples, both on the opposite sides of the spectrum that did not include any alteration to the gene sequence but rather the simple additions of histones to a genome, which caused a drastic change. The first being Angelman syndrome, a disease causing a substantial learning disability and being underweight. This defect is aberrant, as the DNA is perfectly fine, it is only that this person has two epigenetic markings from the mother. The exact opposite can be seen with the prader willi syndrome. This is a form of genetic imprinting and yet we are only here because our epigenetics worked.
Do You Smell What I Smell?
As surprising as it sounds, smelling is a highly personal experience. As Dr Darren Logan explained during the lecture, every person’s perception and understanding of smell is different, all controlled by the specific olfactory neurons that each individual has. These neurons, found partly in the brain and mostly in the nose, are almost like a physical organisation of the outside world inside your head – a world that you recognise largely by the smells it is made up of, and considering the things you smell have a different smell to what the person next to you will smell, we each live in our own world of olfactory senses; this is called specific anosmia.
This almost doesn’t make sense, two people will both describe the same candle similar ways, but in fact they will be smelling two different scents. The reason they recognise it the same way is because compounds with the same chemicals will activate the same olfactory receptors, for example the receptor that picks up a sweet smell will tell your brain the smell is sweet, however the actual scent the receptor is responding to will be different for each person - this is also helped by the fact that most people are very bad at describing smells.
The phenomenon responsible for the different perceptions of smell in different people has been named The Marmite Effect – named because of the controversial opinions Marmite provokes; you either love it or you hate it. To test the theory that the reason that this effect is caused by different receptors, Dr Logan and his team conducted an experiment where 100 people had to smell particular smells of different concentrations, to find the lowest concentration at which each person can detect it. One of their tests showed that a single Olfactory receptor (OR5A1) accounts for 96% of the ability to perceive a specific scented chemical. Not only that, the test also showed that not only does everyone have different receptors, but also different ones that work – meaning the thousands of smells I can’t detect, are different to the thousands someone else can’t.
This is almost scary, considering that every 8 weeks, every single one of the 10 million neurons in your nose dies and is reborn again; meaning that if something went wrong, your perceived sense of smell could completely change, and along with it the world your senses and neurones have created, that is completely unique to you.
Mahwish Ali 12T