The Amazon molly is an unusual all-female fish that reproduces by cloning but has remained genetically healthy and extant for over 100,000 years. This finding challenges the long-held idea that asexual lineages are evolutionary dead ends; earlier models predicted such species would go extinct within 10,000 years.
Researchers Wes Warren and Edward Ricemeyer investigated how the molly persists. Warren produced the first full genome map in 2018 and was surprised to find DNA similar in quality to sexual species. He proposed that gene conversion — the nonreciprocal overwriting of one gene copy by another — might repair and preserve DNA inherited from both parent species.
New long-read sequencing let the team compare the molly’s genome with those of its two parental species and measure mutation patterns. They found the parental genome sets were mutating at different rates, with one side changing faster. The authors concluded gene conversion operates at an apparent optimal rate: it spreads beneficial alleles and removes harmful mutations, producing genetic health comparable to sexual reproduction without males.
- Implications include studying other asexual animals such as Komodo dragons and New Mexico whiptail lizards.
- Findings may inform plant and animal breeding and research into genetic disease and cancer.
- The study appears in Nature; source: University of Missouri.
Difficult words
- asexual — Reproducing without male and female genetic mixing.
- lineage — A sequence of related organisms over time.lineages
- extant — Still existing today; not extinct.
- gene conversion — One DNA copy overwrites another without exchange.
- allele — One version of a gene in a genome.alleles
- mutation — A change in DNA sequence passed on.mutations
- genome — All genetic material in an organism.
- cloning — Creating genetically identical copies of an organism.
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Discussion questions
- Why does the discovery of a long-lived asexual species challenge earlier evolutionary models? Explain with points from the article.
- The article says gene conversion can remove harmful mutations. How might this idea influence research into genetic disease or cancer?
- What further studies would you suggest to check whether gene conversion helps other asexual animals remain genetically healthy?
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