News | Uncovering the 'Selfish Gene': Scientists Use Genomics to Trace Its Evolution and Costs
Selfish genes manipulate the rules of inheritance without regard for the fate of their host. Using population genomics, biologists at the University of Rochester have revealed for the first time how a selfish genetic element called Segregation Distorter (SD) evolved and how it has affected genome structure over time.
The study was led by Amanda Larracuente, an associate professor of biology, and Daven Presgraves, a professor and chair of the Department of Biology, and published in eLife. They found that SD not only changes chromosome organization but also substantially reduces genetic diversity.
First Whole-Genome Sequencing of a Selfish Gene in Fruit Flies
The research team selected fruit flies as its model. These small insects share approximately 70% of disease-related genes with humans and have short reproductive cycles, allowing multiple generations to be produced quickly.
The researchers found that when female fruit flies carry the SD chromosome, approximately 50% of their offspring inherit it, consistent with Mendelian inheritance. Males are very different: they pass the SD chromosome to nearly 100% of their offspring because SD "kills" sperm that do not carry it, effectively monopolizing transmission.
How does SD do this? Research shows that it has evolved into a supergene, a chromosomal region in which multiple selfish genes are tightly linked and inherited together. This structure allows the genes to work as a group, greatly increasing their chance of transmission.
"This is the first whole-genome sequencing of an SD chromosome, allowing us for the first time to reveal the history of this supergene and its far-reaching effects on the genome," Professor Presgraves said.
A Supergene's Short-Term Advantage May Lead to Long-Term Collapse
Although the supergene has a clear short-term advantage, with nearly perfect transmission, researchers found that this advantage comes at the cost of blocking genetic recombination.
During normal sexual reproduction, chromosomes from each parent recombine and exchange genetic material, producing unique offspring. Recombination increases genetic diversity and allows natural selection to remove harmful mutations while retaining beneficial variants.
The SD chromosome does not undergo this recombination. It avoids exchanging genes with the normal chromosome so that it can be inherited as an intact segment. As a result, it becomes a breeding ground for mutations: the study found that SD chromosomes accumulate many more harmful mutations than ordinary chromosomes.
"Without genetic recombination, the SD chromosome cannot use natural selection to remove mutations, and these mutations may impair gene function or regulation," Professor Larracuente explained.
Professor Presgraves further noted that avoiding recombination may be quietly pushing SD toward evolutionary extinction.
"Because it lacks recombination, the SD chromosome is beginning to show signs of evolutionary degeneration," he said.
Why Selfish Genes Matter: From the Microscopic to the Broad View
Research on SD not only reveals how some genes violate the fair rules of inheritance but also shows that short-term evolutionary benefits may carry long-term costs.
More broadly, selfish genetic elements are found throughout the human genome. Some may disrupt sex ratios, affect fertility, increase mutation risks, or accelerate population extinction. A better understanding of these factors may provide important clues for future research on genetic disease and reproductive health.
News | Uncovering the 'Selfish Gene': Scientists Use Genomics to Trace Its Evolution and Costs
News | Uncovering the 'Selfish Gene': Scientists Use Genomics to Trace Its Evolution and Costs
Selfish genes manipulate the rules of inheritance without regard for the fate of their host. Using population genomics, biologists at the University of Rochester have revealed for the first time how a selfish genetic element called Segregation Distorter (SD) evolved and how it has affected genome structure over time.
The study was led by Amanda Larracuente, an associate professor of biology, and Daven Presgraves, a professor and chair of the Department of Biology, and published in eLife. They found that SD not only changes chromosome organization but also substantially reduces genetic diversity.
First Whole-Genome Sequencing of a Selfish Gene in Fruit Flies
The research team selected fruit flies as its model. These small insects share approximately 70% of disease-related genes with humans and have short reproductive cycles, allowing multiple generations to be produced quickly.
The researchers found that when female fruit flies carry the SD chromosome, approximately 50% of their offspring inherit it, consistent with Mendelian inheritance. Males are very different: they pass the SD chromosome to nearly 100% of their offspring because SD "kills" sperm that do not carry it, effectively monopolizing transmission.
How does SD do this? Research shows that it has evolved into a supergene, a chromosomal region in which multiple selfish genes are tightly linked and inherited together. This structure allows the genes to work as a group, greatly increasing their chance of transmission.
"This is the first whole-genome sequencing of an SD chromosome, allowing us for the first time to reveal the history of this supergene and its far-reaching effects on the genome," Professor Presgraves said.
A Supergene's Short-Term Advantage May Lead to Long-Term Collapse
Although the supergene has a clear short-term advantage, with nearly perfect transmission, researchers found that this advantage comes at the cost of blocking genetic recombination.
During normal sexual reproduction, chromosomes from each parent recombine and exchange genetic material, producing unique offspring. Recombination increases genetic diversity and allows natural selection to remove harmful mutations while retaining beneficial variants.
The SD chromosome does not undergo this recombination. It avoids exchanging genes with the normal chromosome so that it can be inherited as an intact segment. As a result, it becomes a breeding ground for mutations: the study found that SD chromosomes accumulate many more harmful mutations than ordinary chromosomes.
"Without genetic recombination, the SD chromosome cannot use natural selection to remove mutations, and these mutations may impair gene function or regulation," Professor Larracuente explained.
Professor Presgraves further noted that avoiding recombination may be quietly pushing SD toward evolutionary extinction.
"Because it lacks recombination, the SD chromosome is beginning to show signs of evolutionary degeneration," he said.
Why Selfish Genes Matter: From the Microscopic to the Broad View
Research on SD not only reveals how some genes violate the fair rules of inheritance but also shows that short-term evolutionary benefits may carry long-term costs.
More broadly, selfish genetic elements are found throughout the human genome. Some may disrupt sex ratios, affect fertility, increase mutation risks, or accelerate population extinction. A better understanding of these factors may provide important clues for future research on genetic disease and reproductive health.
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