Question: Do you think we could force the evolution of genes to benefit ourselves? Do you think we could make them adapt to certain conditions that would make them resistant to all kinds of disease?

Jim Caryl answered on 17 Jun 2011:

I think we probably can, the the question is, what would be the cost?

You see, nature has already resulted in genes that make certain populations of humans resistant to certain diseases. Some African populations suffer from a disease called sickle-cell anaemia, which is a painful and often fatal condition where your blood cells are the wrong shape, so don’t work properly.

You have two copies of every gene in your body, one that you got from your mum, and one that you got from your dad. In order to get sickle-cell anaemia, you would have to get one bad copy of the gene from your mum and also get another bad copy from your dad. However, most children would get one bad copy from one parent, and one normal copy from the other. These people don’t suffer in the same way as those with two bad copies, but do you know what else is interesting about people who only have one bad copy? They are resistant to malaria – the parasite that likes to live inside the blood cells and cause the deadly disease malaria does not like the blood of these people.

So this is the reason why this ‘bad’ gene still exists, because most of the time it makes people resistant to the more common disease of malaria, even though every so often both parents carry one bad copy and one good copy, and if they have four children, one of them will get the deadly sickle-cell disease.

We may find that we create a gene that makes us resistant to one thing, but it may come at the cost of suddenly being more likely to get another type of disease. It is for this reason, amongst others, why we should only focus our attention on repairing the ‘bad’ genes in other genetic disorders, rather than trying to ‘improve’ the genes in already healthy people.