As any decent biologist knows, “nature versus nurture” is a false dichotomy. One way that this is made very clear is with “identical” twins who, though often very similar physically and behaviorally even when raised apart, are nonetheless also notably different from each other even when raised under the same conditions.
Another example is given by the results of cloning, which is more or less the same thing as identical twins, only a generation apart. Even though a clone and donor may be genetically identical, phenotypically they are not. There is noise in the developmental process, some randomness in the regulation of genes, and many ways in which the environment can exert an influence.
In some cases, the distinction between donor and clone can be quite major. Consider, for example, Rainbow and Cc — the first donor and clone cats, respectively. Rainbow is a calico, which introduces another level of complexity as different copies of genes are silenced in different parts of the body. Cc has a completely different coat color pattern. There are also differences in size and demeanor.
I recently completed a similar experiment using one of my cats, Pippin, to note the difference between him and another cat created from samples of his fur (he sheds a tremendous amount).
As with Rainbow and Cc, Pippin’s genetically identical clone differed significantly in body size and temperament.