process information from secondary sources to describe a methodology used in cloning organisms
Background
Cloning is the process of making genetically identical copies of an organism without using the process of sexual reproduction. Both plants and animals have been successfully cloned.
Methodology used in cloning organisms
Recently, plants have been cloned using tissue culture propagation. Tissue from the roots is taken and the root cells separated. These cells are then grown (cultured) in a nutrient-rich medium where they become unspecialised. The unspecialised cells are called calluses. After treatment with the appropriate plant hormones, the calluses are able to develop into seedlings, that go on to grow into fully mature plants. These plants are genetically identical to the original ‘parent’ plant. Rare orchids have been cultured and grown in this manner. A more recent example, has been the cloning of tissue from the Wollemi Pine. This rare pine, thought to be extinct but now has been discovered in the Blue Mountains region of NSWand successfully cloned. These cloned offspring are being cultivated in the Royal Botanic Gardens in Sydney and sold to the public for planting in gardens. Thus, the species, which has few numbers in the wild, can be preserved.
In animals, progress in cloning species has not been as rapid. Current techniques require an unfertilised egg to act as a ‘host’ for genetic material from a specialised cell. The donor egg has had its nucleus physically removed, and the nucleus from a cell of the species to be cloned is inserted. An electrical stimulus is used to fuse the nucleus with the egg cell and to stimulate cell division. At a certain stage in cell division, the embryo is introduced into a surrogate mother where it continues its development. When born the clone is genetically identical to the animal that donated the original nucleus. Cloning of animals was first performed with tadpoles by John Gurdon in the 1970’s. The tadpoles did not survive to grow into adult frogs. Dolly the sheep was the first successfully cloned mammal in 1997. Since then, other species have been cloned.