Gene Drive Technology | Gene Drive Monitor

Synthetic gene drives are a new form of genetic engineering that overcomes the normal rules of inheritance, and which may allow the deliberate eradication or modification of species and populations in the wild.

Gene drives distort the process of inheritance so that the probability of particular genes – and thus specific traits - being passed on is increased substantially above the usual 50% (known as the Mendelian rule of inheritance). Over the course of several generations genes with higher inheritance rates will rapidly spread through a breeding population (see figure 1). Thus, in theory at least, a gene drive can be employed to force genetic changes into an entire population.

Figure 1

How do gene drives work?

Many designs for different gene drives have been proposed, and some have actually been built and tested in laboratories. One of the most well-known gene drive designs is the so called ‘homing gene drive’. In homing gene drives the gene drive sequence can be thought of as ‘copying’ itself from one chromosome to the equivalent location on its partner chromosome (See figure 2). In the process the native genetic sequence is ‘over-written’ by the gene drive sequence. Thus the probability of this ‘drive’ sequence being passed on is increased to nearly 100%. The process of ‘copying’ a sequence from one chromosome to its partner is called ‘homing’ from which the name of this drive design is derived. The homing process is enabled by a genetic sequence derived from bacteria encoding the DNA cutter known as ‘CRISPR-cas9’, which acts to cut the native (i.e. unmodified) sequence.

Figure 2

How might gene drives be used?

The underlying idea of gene drives is to spread a specific trait through wild populations by overriding the rules of inheritance. In the case of gene drives based on CRISPR-cas9 this would be achieved by causing repeated rounds of genetic modification in the wild.

1- Suppression or eradication of wild populations

One common idea is to use gene drives to interfere with the reproduction of a particular species to reduce its numbers, or even to eliminate a population entirely. This could be done by building gene drives that disable vital genes to disrupt reproduction, either by causing sterility or altering sex ratios. For example, homing gene drives have been built in the Mediterranean fruit-fly that disrupt an essential gene for development of females - thus causing offspring to develop as males.

2 - Modification or replacement of wild populations

Another idea is to use gene drives to forcibly introduce new genes into a species thus replacing a wild population with an engineered variant. One idea is to use such drives to modify mosquitoes with additional genes that may limit their capacity to transmit diseases like malaria or Zika.