How do our actions affect our genes?

Chris - Well, the answer is, absolutely it does. There's a number of different ways in which this may happen. If you think about it, I don't know if you go to the gym, but if you go training, you know what happens to your muscles?

Catherine - Yeah.

克里斯-他们变大,对吧?

Catherine - Yes.

Chris - Well, if they're getting bigger, they're growing. If they're growing, they must be producing more of the tissue in a muscle that makes you strong. These are the contractile filaments, actin and myosin. Those are proteins and they get made by turning on a gene that tells our cell how to make them. So, in response to training, in other words, activity, you trigger more genes to get turned on in your muscle cells to make more of the bulk of your muscle. So, there's one really good example of immediately how one of your actions affects your DNA. It affects how active bits of your DNA are. Another example might be for instance in your brain because we know for a fact that when you're subject to certain stresses and strains as you grow up then your brain changes its shape and it puts out connections from one set of cells to another set of cells. Those are controlled by genes and in response to certain long term stresses, we know that certain cells change their behaviour and they upregulate or down regulate. In other words, increase or decrease the production of certain nerve transmitter chemicals. Again, this is a change in response to your activity. And then there's the real kind of far-end of the spectrum which is something we talked about last week on the programme. We talked to Marcus Pembrey who's from Bristol and he did a study looking at fathers who started smoking before the age of 11 and they followed up their children. They found that the sons of those men who started smoking very early were much more likely to become obese in later life compared to individuals who started smoking later and the fathers themselves who were in the study were not obese. So, we couldn't argue it was just something that was a background genetic effect. It seems like there is something changing in the DNA passed on to those offspring from the fathers who smoke in response to their smoking habit. One possibility is a phenomenon called epigenetics. This is where the DNA itself doesn't change, but there are chemical markers added to the outside of the DNA, almost like signposts that can turn genes on or off, or turn the amount that the gene is turned on up or down, and this has an effect. And so, it may be that this smoking habit had the effect on certain genes linked to growth in those children. So, the answer to your question is, absolutely and there are some good examples.