In a message dated 7/6/2004 7:33:09 AM Central Daylight Time, pbs-request@lists.ibiblio.org writes: > >In the scientific sense a clone is two or more individuals that are > >genetically identical. Hi, I cannot say for sure what clone means for all disciplines, or what the original word meant. But, I can quite confidently state that in biology, especially in genetics, "clone" is meant to refer to 2 or more genetically identical individuals. The actual reason they are genetically identical is because the "cloning" process is actual asexual reproduction. Thus, by definition (mitosis) the 2 or more progeny are genetically identical. However, it is clear that some mutations occur during mitosis and organisms propagated through "division" or other methods of "cloning" can sometimes accumulate significant mutations. As near as I can tell, such mutations are very rare (less than 1 in a million or 1 in a billion cell divisions, on average) for most organisms. Thus, while sharp-eyed people can find sports (mutations), and some mutations are propagated accidentally, most descendants of clonal propagation will, on average, be genetically identical to the progenitor--no matter if it existed 200 or 500 years ago. Humans play the role of "natural selection" in this process--and can choose to select apples or bulbs, or whatever, that have pleasing qualities. Thus, rare DNA replication mistakes can lead to variation. Nonetheless, by definition, the modern genetic definition of cloning refers to individuals that are genetically identical, but with enough "fudge factor" to allow for minor variations each generation. Thus, it is clear that cloning leads to production of genetically identical individuals, but also that, sometimes through DNA replication errors, non clones are produced. These "nonclones" may seem identical but may vary in tiny DNA errors or they may have major errors. Another wrinkle to the definition of cloning is that, sometimes, DNA sequences may be faithfully replicated but slight chemical modifications of the DNA (e.g., methylation) may happen (or fail to happen). In this scenario the DNA is the same, and the progeny are genetically identical, but some genes may be silenced (or activated) relative to other genes. Such condition may persist or may be lost in time (e.g., paternal vs. maternal inheritance) and the original "clone" may reappear visually (in terms of what you and I perceive). LINK: one genetical definition of clone http://csu.edu.au/learning/ncgr/… LINK: another definition of clone http://webster-dictionary.org/definition/clone/ LINK: DNA replication, fidelity errors http://pathology.washington.edu/Seminars/info/… LINK: DNA clone, or "molecular clone" http://biochem.northwestern.edu/holmgren/Glossary/… LINK: Epigenetic inheritance http://campusprogram.com/reference/en/… LINK: Organellar inheritance http://ndsu.edu/ndsu/abergstr/… LINK: Maternal inheritance http://ndsu.edu/ndsu/abergstr/… Cordially, Joe, Conroe, TX; where the Crinum are in full flower and leaf, and the mosquitos are as big as crows