Question: Have you ever found any dangerous mutations that could be a threat to the human race if it can spread as a disease?

Claire Shooter answered on 19 Jun 2014:

I’m afraid I only study human genetics, which don’t really work like that: we only pass mutations on through inheritance, so if someone got a really bad mutation they would only spread it to their children.

The mutations that can really threaten humanity are the ones that occur in viruses and bacteria. Both viruses and bacteria are breeding all the time. Occasionally, some will have mutations. The majority of the time – as with humans – these mutations will be damaging and make the virus or bacteria less ‘fit’ to reproduce, so they eventually die off. Occasionally a mutation might make a virus or bacteria better somehow – like more resistant to one of the antibiotics we use to treat them.

This is where they get dangerous: supposing you had a viral infection and took a course of antivirals to kill it…the antivirals are designed to kill everything, but you need to take them for a certain amount of time to ensure that they do. If you decide to stop taking them early (because you feel better, as most of the virus is dead, and you’re sick of taking the pills) you may end up leaving a small amount of the virus – the ones which by chance had a bit of resistance to the antiviral drug – alive, and able to infect other people. The slightly resistant virus breeds in the next person, who, again, takes some antivirals and kills most of them but still doesn’t finish the course. The viruses that have survived now are the fittest of the original slightly resistant group. Eventually, you end up with a new strain of virus which we can’t kill with antivirals and lots of people die. This is why it is important to always finish antibiotic or antiviral courses. Viruses can spread fast and cause huge destruction: an outbreak of Spanish Flu in 1918 killed more people than World War 1.