Genome complexity: Elkhorn coral passes on body mutations (Introduction)

by David Turell , Thursday, January 12, 2023, 18:24 (470 days ago) @ David Turell

Usually only mutations in genetic cells are used:

https://www.the-scientist.com/news-opinion/corals-upend-longstanding-idea-about-genetic...

"Corals native to Caribbean waters may have broken a basic tenet of biology. When a mutation occurs in the body cells of nearly any animal on Earth, it’s not passed on to offspring via reproductive cells. But these corals do pass on such mutations, according to a new study.

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"Baums is also interested in the genetic diversity of corals, so she studies how they reproduce. Elkhorn coral reproduces both sexually and asexually. During asexual reproduction, a portion of the parent coral either breaks or buds off and attaches to the seabed nearby. Sexual reproduction is a bigger event: Every August, shortly after the full moon, all of the corals in a reef sync up to release their reproductive cells at once, which can then merge in the water. Eggs typically require fertilization by sperm from different colonies, then turn into larvae and swim up to hundreds of miles away to establish a new colony. “It’s an absolutely stunning experience,” says Baums. “It looks like it snows, but the wrong way around, from the bottom.”

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"During the process of comparing the genomes of the parent corals with the offspring that arose via self fertilization and the nearby clones that arose via budding, she and her team realized “that this really old clone had accumulated a number of somatic mutations, and those somatic mutations ended up in those [offspring],” she says. Since the corals had self-fertilized, limiting the number of genetic possibilities that could occur in the offspring, the researchers could relatively easily search for somatic mutations. They found 268 somatic mutations in the parent clone, with each nearby clone that arose from the parent sharing between 2 and 149 of these mutations. Around 50 percent of the mutations found in the parent clone also showed up in offspring that were produced via self-fertilization. “It’s really unusual for an animal,” says Baums.

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"Previously, it was thought that in order for mutations to be passed on to offspring in animals, they need to be present in the reproductive or germline cells. Mutations that develop throughout life are thought to remain only in our body cells. Baums says that the researchers aren’t sure how germ cells are acquiring these mutations, but they hypothesize that the somatic cells may have dedifferentiated into stem cells, and then redifferentiated into germ cells.

“'This is an observation we made that’s just really stunning. It’s just unexpected,” Baums says. She says that somatic mutations might be a previously-unrecognized source of genetic diversity for corals, which might influence how they adapt in response to stressors such as ocean warming and acidification. “We really want to understand what evolutionary impact the somatic mutations might have. Are they really a source for novelty and an adaptation for these corals that might be significant, given the huge stressors these corals are exposed to at the moment?'”

Comment: Somatic mutations should not do this, but they did. An odd finding.