Cloning Plants & Animals

4. Cells grow rapidly into small masses of tissue

5. More growth hormones are added to stimulate the growth of roots and stems

Advantages of tissue culture

Disadvantages of tissue culture

A lot of new plants can be grown in a relatively short time

All plants have same genetic make-up - so will all be vulnerable to same diseases or pests

Little space is needed, and conditions can be precisely controlled

No chance of new beneficial characteristics arising by chance

All new plants inherit the same desirable characteristics

No variation means there is a danger of reducing the gene pool

6. The tiny plantlets are transferred into potting trays where they develop into plants

Cloning of plants has many important commercial implications. Successful varieties of plants can be produced commercially on a massive scale in a relatively short space of time, enabling scientists to develop:

* Fast growing crops that give more than one harvest in a year, or

* Crops with better disease-resistant qualities.

Animal cloning

Cloning also takes place naturally in the simpler animals. Amoebas are single-celled protozoa which reproduce by binary fission, resulting in two offspring with identical genes.

Advantages of embryo transplanting

Disadvantages of embryo transplanting

Allows screening for defects in gametes

Does not add variety - so no opportunity for natural selection

Makes it possible to choose sex and time of birth

Lack of hybrid vigour - animals potentially vulnerable to disease

Exact copies of the 'best' animal specimens, year after year

Danger of reducing the gene pool

Could be used for saving endangered species from extinction

Some animal welfare concerns - e.g. about the longevity of cloned animals

. An egg cell was removed from the ovary of an adult female sheep, and the nucleus removed.

2. Using micro-surgical techniques, the empty egg cell was fused with DNA extracted from an udder cell of a donor sheep

3. The fused cell now began to develop normally, using the donated DNA.

4. Before the dividing cells became specialised the embryo was implanted into the uterus of a foster-mother sheep. The result was Dolly, genetically identical to the donor sheep.