Extinct animals can be successfully cloned using preserved DNA
the verdict
REFUTED
the evidence says no
refutedsupported
the weight of evidence
3 sources for · 3 against
Scientific literature indicates that while cloning extinct species using preserved DNA is a theoretical concept, post-mortem DNA degradation and incomplete genomes currently render the successful cloning of long-dead organisms infeasible.
Cloning as it relates to the animal kingdom generally refers to the production of genetically identical individuals. Because cloning is increasingly the subject of renewed attention as a tool for rescuing endangered or extinct species, it seems timely to dissect the role of the numerous reproductive techniques encompassed by this term in animal species conservation. Although cloning is typically associated with somatic cell nuclear transfer, the recent advent of additional techniques that allow genome replication without genetic recombination demands that the use of induced pluripotent stem cells to generate gametes or embryos, as well as older methods such as embryo splitting, all be included in this discussion. Additionally, the phenomenon of natural cloning (e.g., a subset of fish, birds, invertebrates, and reptilian species that reproduce via parthenogenesis) must also be pointed out. Beyond the biology of these techniques are practical considerations and the ethics of using cloning and associated procedures in endangered or extinct species. All of these must be examined in concert to determine whether cloning has a place in species conservation. Therefore, we synthesize progress in cloning and associated techniques and dissect the practical and ethical aspects of these methods as they pertain to endangered species conservation. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 12 is February 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Summary
De‐extinction, the idea that extinct species might soon be resurrected, receives considerable attention in both popular and scientific literature, in particular with regard to its potential ecological and ethical consequences.
Here, I review the three main pathways that are being considered at present for de‐extinction: back‐breeding, cloning via somatic cell nuclear transfer (SCNT) and genetic engineering. I present the state of the art in each pathway and discuss the limitations of each approach as a mechanism to resurrect extinct species.
Back‐breeding aims to concentrate ancestral traits that persist within a population into a single individual using selective breeding. In back‐breeding, ancestral phenotypes may be resurrected after many generations, but the genes that underlie these phenotypes may differ from those that were present in the extinct species.
Cloning aims to create genetically identical copies of an extinct species from preserved somatic cells. These somatic cells are fused with egg cells from a closely related and living donor species, which causes cellular reprogramming and embryogenesis, a scientific process known as SCNT. The developing embryo is then brought to term within a surrogate host. Because biological remains degrade post‐mortem, cloning of long‐dead organisms is not likely to be feasible.
Genetic engineering aims to edit the genome sequence within cells of living species so that these genome sequences closely resemble that of a closely related extinct species. This approach draws on recent advances in both ancient DNA and genome editing technologies and is a particularly promising approach to de‐extinction. After the genome of a living cell is edited, that living cell can then be used for SCNT.
Because the phenotype of an organism is the consequence of the interaction between its genotype and the environment in which it develops and lives, even species with cloned nuclear genomes will not be exact copies of the extinct species on which they are modelled. We should therefore consider de‐extinction as a means to create ecological proxies for extinct species.
A lay summary is available for this article.
Taking into account the latest Red List of the International Union for Conservation of Nature (IUCN) in which 25% of all mammals are threatened with extinction, Somatic Cell Nuclear Transfer (SCNT) could be a beneficial tool and holds a lot of potential for aiding the conservation of endangered, exotic, or even extinct animal species if somatic cells of such animals are available. In the case of shortage and sparse amount of wild animal oocytes, Interspecies Somatic Cell Nuclear transfer (iSCNT), where the recipient ooplasm and donor nucleus are derived from different species, is the alternative SCNT technique. The successful application of iSCNT, resulting in the production of live offspring, was confirmed in several combination of closely related species. When nucleus donor cells and recipient oocytes have been used in many other combinations, very often with a very distant taxonomical relation iSCNT resulted only in the very early stages of cloned embryo development. Problems encountered during iSCNT related to mitochondrial DNA (mtDNA)/genomic DNA incompatibility, mtDNA heteroplasmy, embryonic genome activation (EGA) of the donor nucleus by the recipient oocyte, and availability of suitable foster mothers for iSCNT embryos. Implementing assisted reproductive technologies (ARTs), including iSCNT, to conservation programmes also raises concerns that the production of genetically identical populations might cause problems with inbreeding. The article aims at presenting achievements, limitations, and perspectives of iSCNT in maintaining animal biodiversity.
to resurrect extinct species of dinosaurs by creating cloned creatures using DNA extracted from fossils. The cloned dinosaurs are used to populate the
Cloning is the process of producing individual organisms with identical genomes, by either natural or artificial means. In nature, some organisms produce clones through asexual reproduction; this reproduction of an organism by itself without a mate is known as parthenogenesis. In the field of biotechnology, cloning is the process of creating cloned organisms of cells and of DNA fragments.
The arti
Tadpole: (1952) Robert Briggs and Thomas J. King successfully cloned northern leopard frogs: thirty-five complete embryos and twenty-seven tadpoles from one-hundred and four successful nuclear transfers.
Carp: (1963) In China, embryologist Tong Dizhou produced the world's first cloned fish by inserting the DNA from a cell of a male carp into an egg from a female carp.
Zebrafish: (1981) George Streisinger produced the next in line of the vertebrates.
Sheep: (1984) Steen Willadsen produced the first cloned mammal from early embryonic cells.
In June 1995, the Roslin Institute cloned Megan and Morag from differentiated embryonic cells.
In July 1996, PPL Therapeutics and the Roslin Institute cloned Dolly the sheep from a somatic cell.
Mouse: (1986) A mouse was successfully cloned from an early embryonic cell. In 1987, Soviet scientists Levon Chaylakhyan, Veprencev, Sviridova, and Nikitin cloned Masha, a mouse.
Rhesus monkey: (October 1999) The Oregon National Primate Research Center cloned Tetra from embryo splitting and not nuclear transfer: a process more akin to artificial formation of twins.
Pig: (March 2000) PPL Therapeutics cloned five piglets. By 2014, BGI in China was producing 500 cloned pigs a year to test new medicines.
Gaur: (2001) was the first endangered species cloned.
Cattle:
Alpha and Beta (males, 2001) and (2005), Brazil
In 2023, Chinese scientists reported the cloning of three supercows with a milk productivity "nearly 1.7 times the amount of milk an average cow in the United States produced in 2021" and a plan for 1,000 of such super cows in the near-term. According to a news report "[i]n many countries, including the United States, farmers breed clones with conventional animals to add desirable traits, such as high milk production or disease resistance, into the gene pool".
Cat: CopyCat "CC" (female, late 2001), Little Nicky, 2004, was the first cat cloned for commercial reasons
Rat: Ralph, the first cloned rat (2003)
Mule: Idaho Gem, a john mule born 4 May 2003, was the first horse-family clone.
Horse: Prometea, a Haflinger female born 28 May 2003, was the first horse clone.
Przewalksi's Horse: An ongoing cloning program by the San Diego Zoo…
Three principal methods are under discussion as possible pathways to "true" de-extinction; i.e., back-breeding, cloning, and genetic engineering.<sup>1</sup><sup>,</sup><sup>2</sup> Of these, while the latter approach is most likely to apply to the largest number of extinct species, its potential is constrained by the degree to which the extinct species genome can be reconstructed. We explore this question using the extinct Christmas Island rat (Rattus macleari) as a model, an endemic rat species that was driven extinct between 1898 and 1908.<sup>3-5</sup> We first re-sequenced its genome to an average of >60× coverage, then mapped it to the reference genomes of different Rattus species. We then explored how evolutionary divergence from the extant reference genome affected the fraction of the Christmas Island rat genome that could be recovered. Our analyses show that even when the extremely high-quality Norway brown rat (R. norvegicus) is used as a reference, nearly 5% of the genome sequence is unrecoverable, with 1,661 genes recovered at lower than 90% completeness, and 26 completely absent. Furthermore, we find the distribution of regions affected is not random, but for example, if 90% completeness is used as the cutoff, genes related to immune response and olfaction are excessively affected. Ultimately, our approach demonstrates the importance of applying similar analyses to candidates for de-extinction through genome editing in order to provide critical baseline information about how representative the edited form would be of the extinct species.
The recent creation of dire wolf-like canids by Colossal Biosciences marks a technical achievement in genome editing and synthetic embryology. But the project also demands a reevaluation of what we mean by "de-extinction"-and whether a phenotypic approximation constitutes species restoration.
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