The genome of the critically endangered mountain gorilla provides clues to its genetic past as well as its prospects for future survival.
Gorilla family trees. I’m Bob Hirshon and this is Science Update.
The mountain gorilla is critically endangered, with fewer than 900 remaining in the wild. Now, scientists have sequenced the great ape’s genome for the first time in order to assess its genetic health. Chris Tyler-Smith is with the Wellcome Trust Sanger Institute.
We found that in the mountain gorillas the levels of genetic diversity were very low. For roughly a third of the genome of each individual there’s no variation at all; they’ve inherited identical copies of that region of the genome from both their mother and their father.
But there’s hope for the gorillas yet: Tyler-Smith and his colleagues write in the journal Science that while inbreeding can be harmful, there’s evidence that the gorillas have coped with it for thousands of generations. What’s more, the most harmful mutations have been removed from the gene pool by natural selection. I’m Bob Hirshon, for AAAS, the science society.
Making Sense of the Research
Many of us are familiar with mountain gorillas through the work of scientists like Dian Fossey. These gorillas are actually a subspecies of the eastern gorilla and they live in the Virunga Mountains, a range of extinct volcanoes that border the Democratic Republic of Congo, Rwanda, and Uganda, and in the Bwindi Impenetrable National Park in Uganda. This species is considered critically endangered, with a population of approximately 880 individuals in the wild. This figure, however, is up from a low of 620 animals in 1989.
Scientists studying the threats to the mountain gorillas' survival, which include human actions like war, habitat loss, poaching, and disease, have long wondered how inbreeding among the gorillas affects their survival. This first in-depth whole-genome analysis of the gorillas by Chris Tyler-Smith and his colleagues suggests that many harmful genetic variations had been eliminated through inbreeding and that mountain gorillas are genetically adapting to surviving in small populations. According to study corresponding author Aylwyn Scally, of the department of genetics at the University of Cambridge in England, "This new understanding of genetic diversity and demographic history among gorilla populations provides us with valuable insight into how apes and humans, their closely related cousins, adapt genetically to living in small populations."
To conduct this research, the scientists used blood samples collected over several years by the Rwanda Development Board, The Institut Congolese pour la Conservation du Nature, and Gorilla Doctors. With these blood samples, they were able to sequence the whole genomes of seven mountain gorillas. The blood samples showed that the mountain gorillas were less genetically diverse than gorillas in larger populations in western regions of central Africa.
Despite the potential problems that inbreeding could cause, like an increase of threats from disease and environmental change due to a reduced genetic ability to adapt, it seems that inbreeding has provided some benefits to the mountain gorillas: namely, there are fewer harmful loss-of-function variants in the mountain gorilla population than in the more numerous western gorilla populations. These variants stop genes from working and can cause serious, often fatal, health conditions. Scientists also discovered that the mountain gorillas have survived in small numbers for thousands of years.
It is hoped that this work on the mountain gorilla genome will aid in conservation efforts by making it easier to identify the origins of gorillas that have been illegally captured or killed.
Now try and answer these questions:
- Where do the mountain gorillas live?
- Why did scientists want to map the genome of the mountain gorilla?
- What are some of the threats to the mountain gorillas' survival?
- What did the scientists find when they sequenced the mountain gorilla's genome?
- What are some problems that could be caused by inbreeding? How has inbreeding helped the mountain gorillas?
You can check out the Science news article called Mountain gorilla genome provides hope for animal's future to learn more about this research.
The Science Update Genes and Geography looks at a study of genetic variation in which the differences between populations aren't as dramatic as the researchers expected.
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This fascinating story about the sequencing of the mountain gorilla genome and what it helped scientists discover about the survival of these gorillas can help to engage your students in the study of genomes and genetic variation. You can use this resource to help supplement lessons on genetic variation and natural selection.
In addition, the Platypus Genome Science Update can help your students learn how scientists have sequenced the genetic code of one of nature's strangest animals.