What Is a Clone in Biology?
Before pop culture gets to the word, biology already has several precise meanings for “clone” — covering DNA, cells, and whole organisms.
In ordinary speech, “clone” usually means a duplicate person. In biology, the word is older and broader. Knowing the biological definition makes most cloning coverage easier to parse.
The general definition
A clone is an organism, cell, or stretch of DNA that is genetically identical, or nearly identical, to another. The relationship can be created in a laboratory or can happen naturally. A cutting from a strawberry plant that has been propagated vegetatively is a clone. So is one of a pair of identical twins. So is a stretch of DNA that has been copied inside a bacterium.
The three main kinds
DNA clones
A DNA clone is a copy of a specific stretch of genetic material, typically maintained inside a host cell. Gene cloning is the most common laboratory application of this idea. Most molecular biology depends on it.
Cell clones
A cell clone is a population of cells derived from a single parent cell, sharing essentially the same genome. Cell lines used in biomedical research are usually clones in this sense.
Organismal clones
An organismal clone is a whole organism genetically very similar to another. Identical twins are natural clones of each other. Dolly the sheep was an organismal clone of the sheep that donated the body-cell nucleus. Many plants reproduce clonally as a matter of course.
What clones do not share
Even an organismal clone is not a duplicate in every sense. Several things tend to differ:
- Mitochondrial DNA. In cloning by nuclear transfer, mitochondrial DNA comes from the donor egg, not the nuclear donor.
- Epigenetic marks. The chemical tags that switch genes on and off accumulate over time and respond to environment.
- Developmental conditions. Cells, tissues, and organisms develop under conditions that shape outcomes in ways DNA alone does not predict.
- Experience. For organisms with brains, experience is most of what produces personality.
Key takeaway
In biology, “clone” covers DNA, cells, and organisms. Sharing DNA is not the same as being identical in every sense, and biology has known that for a long time.