CLONING: Cloning is a technique in which identical copies are produced by asexual means. A cell or individual and all its asexually produced off springs.
EXPLANATION: All members of a clone are genetically identical except when a mutation occurs.
In 1997 scientists in Scotland succeeded in cloning a sheep (dolly). Other mammalian species (mice and cows) have since been cloned.
Cloning is not a natural process. Several insects and many plants do it occasionally. However few do so regularly.
A clone is produced by the following procedures:
PROCEDURE-I: The nucleus from a fertilized egg is removed and a nucleus from a cell of a fully developed individual is inserted in its place.
The altered zygote is then fixed in a suitable womb where it completes its development.
The new individual formed in this way is a genetically identical clone of the individual whose nucleus was used. Therefore by cloning, many copies of a desired génotype are made.
In 1997 scientists in Scotland succeeded in cloning a sheep (dolly) by this procedure. Other mammalian species (mice and cows) have since been cloned.
PROCEDURE-II (DEVELOPMENT OF IDENTICAL TWINS BY CLONING):
Here a single egg or early embryo is divided into one or more separate embryos. The process is like the production of identical twins.
The offspring from this type of cloning are genetically identical but carry chromosomes from both parents.
This type of cloning is used to produce genetically identical cattle and other farm animals.
IMPORTANCE OF CLONING:
(i) Cloning is a technology for achieving eugenic aims.
(ii) Man is trying to start cloning — techniques for commercial production of valuable animals like horses, cows, sheep etc.
(iii) At some places scientists are trying to clone human embryo which can serve as transplant donor. In this way cloning is important in fighting diseases.
However there is controversy on the issue of human cloning.