F215 control, genomes and environment Module 2 – Biotechnology and gene technologies

Learning Outcomes  Describe the production of natural clones in plants using the example of vegetative propagation in elm trees.  Describe the production of artificial clones of plants from tissue culture.  Discuss the advantages and disadvantages of plant cloning in agriculture.

Cloning  Cloning is the production of genetically identical organisms  In plants cloning can occur naturally by asexual reproduction.  All cells are produced by mitosis from cells that were originally part of the parent plant  All plants are genetically identical to the parent plant and each other.

Asexual reproduction  Advantages  Quick  All offspring have the genetic information to enable them to survive in the environment  Disadvantages  No genetic variety  Does not allow for natural selection  Unable to adapt to environmental conditions.

Vegetative propagation  Asexual reproduction in plants is known as vegetative propagation  Examples ▪ Strawberry plants produce runners ▪ Potatoes form underground tubers ▪ Daffodils produce bulbs ▪ English Elm produces root suckers (basal sprouts)

Vegetative propagation in potatoes

English Elm  The English Elm only reproduces by suckering  The growth of new trees from the roots or meristem tissue in the trunks  As all English Elms are genetically identical they are all susceptible to the fungus, Dutch elm disease

Artificial Vegetative propagation  It is possible to artificially propagate valuable plants  Taking cuttings – cut a section of stem between nodes, then treat with plant hormones to encourage root growth  Grafting – a shoot section of a woody stem is joined to a root stock  Tissue culture

Grafting

Tissue Culture  Tissue culture allows for the production of huge numbers of genetically identical plants from a small amount of plant material.  All stages in tissue culture must be carried out in sterile conditions to prevent fungal infection

Stages in Plant Tissue Culture  A group of cells are removed from the parent plant called the explant.  Explant is placed on a nutrient growth medium  Cells divide to form a mass of undifferentiated cells called a callus  Single cells removed from callus and placed on a growth medium to stimulate shoot growth  The shoots are placed on a growth medium to stimulate root growth  Growing plants transferred to a greenhouse before planting outside

Plant Cloning in Agriculture  Desirable parent plant can be chosen and cloned  Plants mature at same time  In UK, Annual crops are propagated by seed  After years of inbreeding all crops are now genetically uniform  Even though seeds require sexual reproduction, all seeds and plants produced are genetically uniform

Plant Cloning in Agriculture  In perennial plants, the high cost of vegetative propagation is offset by  the long periods for which the plants stay in the ground  Relatively high value of the product  Examples  Lavender  Apple trees

Disadvantages of plant cloning  Susceptible to disease  Unable to adapt to climate change  Loss of genetic variation

Learning Outcomes  Outline the differences between reproductive and non-reproductive cloning.

Cloning in Animals  Reproductive cloning  Cloning to produce a whole organism  Examples ▪ Embryo transplantation ▪ Dolly the sheep  Non-reproductive cloning  Using cloning to produce cells  Examples ▪ Stem cell research ▪ Production of cells, tissues or organs

Non-reproductive cloning in animals  Non-reproductive cloning involves the production of genetically identical cells  1951 – HeLa cells ▪ Cancerous cells which divide repeatedly in culture solution ▪ Used in medical research  Stem cells ▪ Totipotent or pluripotent ▪ Undifferentiated cells that are able to differentiate into specialised cells ▪ Embryonic stem cells – ethical arguments

Possibilities of non-reproductive cloning  Potential future uses include  Regeneration of heart tissue following a heart attack  Repair of nervous tissue  Repairing the spinal cord  Stem cells taken from the patient to produce the tissues mean that tissue rejection by the immune system is less likely

Learning Outcomes  Describe how artificial clones of animals can be produced.  Discuss the advantages and disadvantages of cloning animals.

Reproductive cloning in animals  Two methods of artificially cloning animals  Splitting embryos for embryo transplantation ▪ All offspring are identical to each other but not to the surrogate mothers  Nuclear transfer using enucleated eggs ▪ Nucleus is taken from a differentiated cell in an adult, and placed into a enucleated egg cell

Dolly the Sheep  Dolly the sheep is believed to have suffered from a serious health problem which developed at a relatively early age

Artificial Cloning in animals  Advantages  High value animals  Rare animals can be cloned  Quickly reproduced  Disadvantages  Animal welfare  Genetic uniformity, loss of genetic variation  Uncertainties of health of cloned animals Moral and ethical Arguments  Is it right to clone an aging pet?  Is it right to clone an animal which leads to a cure for human diseases?