which has an easily identifiable phenotype
so that one can tell apart cells or individuals which have the gene
and those which do not have it. Such a gene can also be used as a probe to mark cell nuclei
s so that they can easily be isolated or identified from other nuclei or chromosomes later.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.