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Q44 - Gene Drive Technology

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Recombinant DNA & Biotechnology Techniques Sex Determination & Sex-Linked Inheritance

Gene drives (mutagenic chain reaction) are a modern technology which causes highly efficient conversion of wild type alleles to non-functional alleles in all progeny of a carrier.

Gene drives are based on a transgenic construct containing genes of a target-locus-specific guideRNA (gRNA) and Cas9 RNA-guided DNase. If this transgenic construct co-occurs in a cell with the wild type target locus, Cas9 cleaves the target DNA. Next, a copy of the construct is inserted into the target locus by the homology directed repair (HDR) mechanism. This transgene insertion disrupts the target locus and leads to a loss-of-function mutation (see the figure).

Initially gene drive technology was tested on fruit flies. The mutagenic construct yellowmut was integrated into the X-linked gene yellow; loss-of-function in yellow leads to the flies having yellow bodies (wildtype flies have brown bodies). The Y-chromosome does not contain a copy of the gene yellow.

Assume sex is determined in the same way as in humans.

Gene drive mechanism: expression, cleavage, and homology-directed repair inserting construct into target locus

True or false?

Q44.1. All progeny of yellow males will have yellow bodies.
Q44.2. All progenies of yellowmut / yellowmut females will have yellow bodies.
Q44.3. Gene drives targeting genes involved in sex determination and reproduction could become an efficient tool in pest insect population control.
Q44.4. Lethal loss-of-function mutations could be successfully introduced in insect populations by gene drive technology.
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Question reproduced from IBO 2023, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF