cloning /klō″ning/ , a procedure for producing multiple copies of genetically identical organisms or cells or of individual genes. Organisms may be cloned by transplanting blastocysts from one embryo into an empty zona pellucida, or nuclei from the cells of one individual into enucleated oocytes. Cells may be cloned by growing them in culture under conditions that promote cell reproduction. Genes may be cloned by isolating them from the genome of one organism and incorporating them into the genome of an asexually reproducing organism, such as a bacterium or a yeast.
