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Unzip your genes - Debate the influences on characteristics

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Join the discussion: So there are genetic and environmental influences on our characteristics. But is it really that simple? Perhaps our genes can influence our environment, or vice versa?

24 Mar
2011

So there are genetic and environmental influences on our characteristics. But is it really that simple? Perhaps our genes can influence our environment, or vice versa?

For the purpose of the quiz we have kept it quite straightforward and focused on the relative influences of genes and environment separately. But the more research we do, the more we know that most of our characteristics aren't simple at all! Most of our traits are complex, and influenced by many different genes and many different environmental influences.

Some influences of what we perceive to be 'environmental' actually also have a genetic component. You may have thought of smoking as an environmental component, but whether people quit smoking or persist in their behavior is actually strongly influenced by their genes.

Genes can interact with each other. For example, if gene A contributes a 2% risk, gene B a 3% risk, together they may contribute a higher risk than the simple sum of their risks. These gene-gene interactions are also studied in twin and family studies, but were not discussed in the quiz.

And to make things even more complex there may also be interactions between genes and environment. The effect of a particular environmental factor might depend on someone's genetic make-up. A traumatic life event may be especially influential for people who carry a particular gene variant that makes them susceptible to depression. Our understanding of how gene effects interact, and how gene and environmental factors interact is still relatively poor.

What do you think?

If this has sparked your interest, why not join in the discussion by posting a response in the Comments section below?

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Human behaviour and genetic programming

Ken Natton

This is a subject that is of great interest to me, though I should declare that I am neither a qualified life scientist, nor a formal student of life sciences. I used to engage with the old Open2 forums and I learned a great deal from that. One of the things I encountered through that was this new science they call evo-devo, evolutionary development. Surely one of the key lessons from that, if we begin by taking a simple morphological trait of a species, is that it is unlikely that only one gene is involved in the making of that trait. There are probably several genes involved, possibly dozens. But even if you were to do the hard scientific work and successfully isolate every single gene involved in the making of that morphological trait, still you wouldn’t have the answer as to exactly how that trait was made. You would still have to investigate the embryological process to understand the precise sequence in which those genes were expressed, how the expression of one protein stimulated the expression of another in a long and very complex sequence. In the same way that it is the sequence of amino acids within the protein that govern how it folds and thus what its properties are, so it is the sequence of gene expression that governs the observable phenotypic trait.

So if you think about a behavioural trait, surely that also is likely to involve multiple genes and complex sequences of expression? It always seems to me to be a fundamental misunderstanding when I hear someone talk of ‘a gene for alcholism’ or ‘a thrill seeking gene’ or ‘a criminal gene’. Beyond the nature / nurture debate, it is clear that many human behaviours are genetically programmed, but even the most advanced life science does not yet understand exactly how that works – even in terms of generic principles, let alone the specifics of one particular behavioural trait. I recognise that it is not particularly scientific to talk about what you do and don’t believe, but it does seem to me that some aspects of human behaviour go beyond the merely genetically programmed. Far from criminality being in the genes, what an individual’s genes give them is the ability to recognise the harm that they do and to make a choice about whether or not to do that harm. And into this complexity you can add this two way influence between genes and environment that Dr Hoekstra and Dr Hirst talk about. I am always wary of over playing what science does not know. Life scientists do know a great deal and have achieved the most astonishing things. I know that I have barely scratched the surface of what modern life scientists do know. But my impression is that we are a long way from the true scientific answers to these questions, and I am not entirely convinced that we will ever really know them. I am aware of those physical scientists of far deeper knowledge than me that argue that every human decision can ultimately be explained in terms of the quantum physical interactions that govern chemical activity in the brain. I am not convinced that human beings are quite that clockwork. Who knows, I am here to be surprised and believe me, I am watching this space.

The Unzip Your Genes Quiz

Jody Hodgson

A number of questions in this quiz I felt were a little bias, were as I am no Genologist I do see myself as a fairly intellegent and sensible person.

The is smoking inheritable seems a little wrong, whereas I agree the addictiveness to smoking may be genetic I find it highly dubious that smoking itself is a inheritable trait.

Again with the "How heritable is breast cancer?" question surely the development of breast cancer is genetic not the actual event.

Likewise with "How heritable is extroversion?" surely this has got to be more of a social and nurture based trait that "switches" this trait into activity and not purely down to genetics.

Surely this would be like saying that intelligence or sexual preference is inheritable.

I appreciate the quiz was aimed at been kept quite simple but I would debate that the type of person that watched the BBC show that led them to this site would be expecting a little more from the quiz.

Genetics of smoking

Rosa Hoekstra

Hi Jody,

Thanks for your comment. You are absolutely right that the addiction to smoking is more heritable than whether you take up smoking or not. The percentage mentioned in the quiz reflects the relative genetic influences on the addiction to nicotine: this is highly heritable. Some people are much more addicted to nicotine than others (they may for instance have their first cigarette of the day first thing in the morning, whilst others only smoke now and then, in the evening). These individual differences in smoking addiction are mainly explained by genetic effects. Whether someone takes up smoking in the first place is much more strongly influenced by your environment. As explained in the quiz’ results, having family members and friends who smoke are important predictors for the uptake of regular smoking. Healthy life style choices, such as limited alcohol intake, or frequent sports participation, make it less likely that people take up smoking.

I hope this clarfies things.

best wishes, Rosa Hoekstra
Lecturer in biological psychology and genetics at the OU

Article Information

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Thursday, 17th February 2011
Thursday, 24th March 2011

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