Cloning, an asexual method of reproduction, produces an individual with the same genetic material (DNA) as another individual. Probably the best-known examples of clones are identical twins, which result when cells in the early development stage separate and develop into different individuals. Though the DNA in cloned individuals is the same, environmental influences may make them differ in phenotype. Thus far, the commercial use of clones has been limited. Cloning can be used to produce clones from a highly productive individual, but the cost would have to be low enough to recover the expense quickly. Animals have been cloned by three processes: embryo splitting, blastomere dispersal, and nuclear transfer. Nuclear transfer is most common and involves enucleating an ovum, or egg, with all the genetic material removed. This material is replaced with a full set of chromosomes from a suitable donor cell, which is microinjected into the enucleated cell. Then the enucleated cell, with the transplanted chromosome, is placed into a recipient female to be carried through gestation.
Red-Poll-cow-and-calfRed Poll cow and calf.[Credits : © J.C. Allen and Son]
Thoroughbred-stallion-with-dark-bay-coatThoroughbred stallion with dark bay coat.[Credits : © Scott Smudsky]
The-mouse-at-bottom-is-heterozygous-with-a-mutant-geneThe mouse at bottom is heterozygous with a mutant gene that gives it a spotted tail. The two mice …[Credits : Inserm U636]
Black-Angus-bullBlack Angus bull.[Credits : Henry Elder/Encyclopædia Britannica, Inc.]
Female-pigs-can-have-as-many-as-20-piglets-inFemale pigs can have as many as 20 piglets in a litter. China holds the record for having the …[Credits : © Corbis]
German-shepherdGerman shepherd (Alsatian).[Credits : © Sally Anne Thompson/Animal Photography]
Holstein-Friesian-cowHolstein-Friesian cow.[Credits : Henry Elder/Encyclopædia Britannica, Inc.]
Duroc-boarDuroc boar.[Credits : Grant Heilman Photography]
Link to this article and share the full text with the readers of your Web site or blog-post.
If you think a reference to this article on "animal breeding" will enhance your Web site,
blog-post, or any other web-content, then feel free to link to this article,
and your readers will gain full access to the full article, even if they do not subscribe to our service.
You may want to use the HTML code fragment provided below.
We welcome your comments. Any revisions or updates suggested for this article will be reviewed by our editorial staff. Contact us here.
Regular users of Britannica may notice that this comments feature is less robust than in the past. This is only temporary, while we make the transition to a dramatically new and richer site. The functionality of the system will be restored soon.