Within the same butterfly species, many different wing patterns can occur. How is this possible? According to researchers Ben Wielstra and Emma Berdan, from the Institute of Biology Leiden (IBL), the answer lies in supergenes. A supergene is part of a chromosome that contains many strongly linked genes. Together, these genes form the basis of complex traits in plants and animals.
“The idea of supergenes is relatively old. Only now, with today’s modern DNA techniques, can we map them properly. Recently, it has become clear that supergenes are much more common than previously thought,” says Wielstra. On June 13, Wielstra and postdoc Emma Berdan will publish a special issue on supergenes in Scientific Journal the Philosophical Transactions of the Royal Society B: Biological Sciences.
What are supergenes?
“Super genes are parts of chromosomes that contain several genes that are inherited as a whole,” explains Wielstra. What makes supergenes remarkable is the absence of recombination. Recombination is the mixing of the genetic information from two parents so that offspring are provided with a unique set of chromosomes. “Because there is no recombination within supergenes, all genes within it develop together as a unit. This allows different versions of supergenes to occur within a species, leading to large differences in appearance and behavior.”
Supergenes can occur in different ways. “There are areas in the genome where recombination naturally occurs less frequently. At the same time, recombination can also be stopped, when, for example, the structure of the genome changes.” A well-known example of this is an inversion. Part of the chromosome is broken off and turned so that the order of the genes no longer corresponds to the original. Recombination is then no longer possible.
Ruffen as an example
The presence of supergenes leads to more variation within a species. “My favorite example is the ruff. In these birds, supergenes ensure that the males either have dark or white feathers around the head. There are also males that do not develop a feather collar at all and look like females. These three types of male ruffs not only differ from each other in appearance, but they also behave differently during mating season“, says Wielstra.
Does this provide an evolutionary advantage?
“Sometimes. On the one hand, variation within a species is useful. It allows species to switch between different survival strategies,” explains Wielstra. According to him, supergenes can facilitate this process. But not without price. “Without recombination, harmful mutations can quickly accumulate.” In the crown water salamander, which Wielstra and Berdan have researched, the accumulation of mutations in a supergene has resulted in half of the salamander eggs being unsuitable. “This supergene can be seen as a very extreme example of a hereditary disease,” says Wielstra.
“Super genes are hot”
By studying the development of supergenes, the researchers hope to gain more insight into the origins of hereditary diseases. Even in humans. “Supergenes are hot. More research is being done on this topic than ever before. Therefore, we continue to find more and more examples where large differences in behavior and appearance are affected by a single supergen“With the special issue on supergenes, Wielstra and Berdan hope to be able to give a good overview of the current state of research in this area. Wielstra says:” We now know that supergenes often occur. The next step is to find out exactly how they occur. ”
Emma L. Berdan et al, Genomic architecture of supergenes: connecting form and function, Philosophical Transactions of the Royal Society B: Biological Sciences (2022). DOI: 10.1098 / rstb.2021.0192
Quote: Supergenes make bizarre properties in plants and animals possible (2022, 14 June) Retrieved 14 June 2022 from https://phys.org/news/2022-06-supergenes-bizarre-traits-animals.html
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