B3 - Cloning

• Dolly the sheep was produced by a process called nuclear transfer. This involves removing the nucleus from a body cell and placing it into an egg cell that has had it's nucleus removed.
• Animals could be cloned to:

- mass-produce animals with desirable characteristics

- produce animals that have been ge to produce human products

- produce human embryos to supply stem cells for therapy.

• Dolly steps:

- The donor egg had it's nucleus removed

- the egg cell nucleus was replaced with nucleus from an udder cell

- egg cell was then given electric shock to make it divide

- Embryo was impanted into surrogate mother sheep

• Producing cloned plants has advantages and disadvantages

- Advantages: growers can be sure of the characteristics of the plant as it is a clone so will be genetically identical. Also mass-production may be possible for plants that may be diffult to grow from a seed.

- Disadvantage: Lack of variation. If plant become diseased it will affect all plants.

• Plants can be cloned by a proccess called tissue culture, as follows:

- A plant is selected that has specific characteristics

- A large number of small pieces of tissue are then cut from plant

- The small pieces of tissue are then grown in test tubes containing a growth medium.

- Aseptic technique is used at all stages to stop any microbes infecting the plants.

• Cloning plants is easier than cloning animals, because plant cell retain the ability to differentiate. Animal cells often lose this ability at an early stage.