Picture a lion: The male has a luxuriant mane, the female doesn’t. This is a classic example of what biologists call sexual dimorphism – the two sexes of the same species exhibit differences in form or behavior. Male and female lions pretty much share the same genetic information, but look quite different.
We’re used to thinking of genes as responsible for the traits an organism develops. But different forms of a trait – mane or no mane – can arise from practically identical genetic information. Further, traits are not all equally sexually dimorphic. While the tails of peacocks and peahens are extremely different, their feet, for example, are pretty much the same.
Understanding how this variation of form – what geneticists call phenotypic variation – arises is crucial to answering several scientific questions, including how novel traits appear during evolution and how complex diseases emerge during a lifetime.
So researchers have taken a closer look at the genome, looking for the genes responsible for differences between sexes and between traits within one sex. The key to these sexually dimorphic traits appears to be a kind of protein called a transcription factor, whose job it is to turn genes “on” and “off.”
In our own work with dung beetles, my colleagues and I are untangling how these transcription factors actually lead to the different traits we see in males and females. A lot of it has to do with something called “alternative gene splicing” – a phenomenon that allows a single gene to encode for different proteins, depending on how the building blocks are joined together.
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