It used to be that seeing a mouse in the house was a rare occurrence. Now it's rarely a day that goes by where we aren't seeing or hearing the little vermin.
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Current methods of baiting and trapping are struggling to control the plague of mice spreading across regional Australia. But a $1.8 million investment from the NSW Government might soon give us a new weapon in the war. The Government is investing in research into the use of gene drives, or "selfish DNA" - a genetic tool that can help us to control pests.
How? Well, to understand gene drives we first need to understand the normal way in which genes are inherited. Mice, like humans, have two copies of each gene, one inherited from their mother and one from their father.
We call these copies alleles, and they can be exactly the same or slightly different from each other. Normally, there is a 50/50 chance as to which allele will be passed on to any offspring. If one allele carries some sort of mutation, there is a 50 percent chance that it will be passed on.
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Gene drives hack this normal system of inheritance. When an animal carrying a gene drive mates with another animal that isn't, their offspring will inherit one gene drive allele and one normal allele.
The gene drive then works kind of like a molecular copy and paste system. Gene drives can copy and paste themselves, changing the normal allele into a second gene drive allele. There is then a 100 percent chance, not a 50 percent chance, for that animal to pass the gene drive allele to their offspring.
Every time the gene drive allele is passed on it's replicated - and it quickly spreads through a population. How does this solve our mouse issue?
A genetically engineered gene drive can be used to spread specific genetic mutations. These targeted mutations could make mice infertile. They could also be mutations that change the balance of males and females produced.
In either case, the aim is to spread these mutations, interrupt the breeding cycle and help keep mouse numbers at a manageable level.
This kind of technology is already being developed to control disease-spreading pests like mosquitos.
Soon we'll see if selfish genes are the silver bullet that can also control rapidly reproducing rodents.
Dr Mary McMillan is a senior lecturer at the School of Science and Technology, University of New England
