Biology: Biotechnology and Gene Technologies

outline the differences between reproductive and non-reproductive cloning

Reproductive cloning is the production of offspring which are genetically identical to either the mother (nuclear transfer), or the other offspring (splitting embryos)

Non-reproductive cloning is the use of stem cells in order to generate replacement cells, tissues or organs which may be used to treat particular diseases or conditions of humans

describe the production of natural clones in plants using the example of vegetative propagation in elm trees

The English Elm is adapted to reproduce asexually following damage to the parent plant.

New growth in the form of basal sprouts appears within two months of the destruction of the main trunk.

These suckers grow from meristem tissue in the trunk close to the ground where the least damage is likely to have occurred.

describe the production of artificial clones of plants from tissue culture

A small piece of tissue is taken from the plant to be cloned, usually from the shoot tip- this is called the explant

The explant is placed on a nutrient growth medium

Cells in the tissue divide but do not differentiate. Instead they form a mass of undifferentiated cells called a callus

After a few weeks, single callus cells can be removed from the mass and placed on a growing medium containing plant hormones that encourage shoot growth

After a further few weeks, the growing shoots are transferred onto a different growing medium that encourages root growth

The growing plants are then transferred to a greenhouse to be acclimatised and grown further before they are planted outside

discuss the advantages and disadvantages of plant cloning in agriculture

Advantages 

• Very many genetically identical plants can be

produced from one original plant

• Plants can be produced at any time of the year and

air-freighted around the world

• Callus can be genetically engineered

Disadvantages

• Because all of the plants are genetically identical, they

are all susceptible to a newly mutated pathogen or

pest, or to changing environmental conditions

• The process is labour intensive- it is more difficult to

plant plantlets than to sow seed

describe how artificial clones of animals can be produced

Nuclear transfer

A nucleus from an adult differentiated cell is placed in an enucleated egg cell. The egg then goes through the stages of development using the genetic information from the inserted nucleus

Splitting embryos

Cells from a developing embryo are separated out, with each one going on to produce a separate, genetically identical organism

discuss the advantages and disadvantages of cloning animals

Advantages 

• High value animals, e.g. cows giving a high milk yield, can be cloned in high numbers

• Rare animals can be cloned to preserve the species As with plants, excessive genetic uniformity in a species makes it unlikely to be able to cope with, or adapt to, changes in the environment

• Genetically modified animals- e.g. sheep that produce pharmaceutical chemicals in their milk- can be quickly reproduced

Disadvantages

• High value animals are not necessarily produced with animal welfare in mind. Some strains of meat producing chickens have been developed that are unable to walk

• As with plants, excessive genetic uniformity in a species makes it unlikely to be able to cope with, or adapt to, changes in the environment

• It is still unclear whether animals cloned using the nuclea material of adult cells will remain healthy in the long term