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Tiny changes in gene expression can lead to big differences in eye size

26 February 2025
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A close up of a fly's eye. The is red and you can see the hexagonal components of the eye.

We’re part of an international team of scientists which has discovered that tiny changes in the timing of the expression of a single gene can lead to big differences in eye size.

Gene expression is the process by which the information encoded in a gene is turned into a functional output, for example the production of a protein.

Researchers including Professor Alistair McGregor, in our Department of Biosciences, looked at two closely related species of fruit fly - Drosophila mauritiana and Drosophila simulans.

Timing of expression

They found that a slight change in the timing of expression of a gene called orthodenticle (otd) can cause a significant difference in the size of the ommatidia, the individual hexagonal units that make up a compound eye.

In Drosophila mauritiana, otd is expressed earlier in eye development than in Drosophila simulans.

This associated with in an increase in the ommatidia size of Drosophila mauritiana, meaning the eyes of this species are larger.   

Insects exhibit extensive variation in the shape and size of their eyes, which contributes to adaptive differences in their vision. Our study comparing Drosophila species that differ in eye size reveals one of the genetic mechanisms that can make the facets of their eyes bigger and potentially allow greater contrast sensitivity.
Professor Alistair McGregor
Department of Biosciences

How other organs evolve

The researchers say their findings could have implications for our understanding of how the size of other organs evolve.

They are now planning to investigate whether similar changes in gene expression can lead to differences in the size of other organs.

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