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Micropropagation and cloning animals
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Cloning makes genetically identical copies. It can be done with plants and with mammals.
Micropropagation (tissue culture)
Small pieces of tissue called explants are cut from a plant, often from shoot tips.
They are sterilised and grown in vitro (in glass containers) on a sterile medium containing nutrients and plant hormones.
They develop into tiny plantlets, which are moved into compost to grow.
They are sterilised and grown in vitro (in glass containers) on a sterile medium containing nutrients and plant hormones.
They develop into tiny plantlets, which are moved into compost to grow.
Why growers use it
It produces commercial quantities of genetically identical plants with desirable characteristics (for example, a valuable flower colour).
It is quick, works all year round and needs little space.
It is quick, works all year round and needs little space.
Cloning a mammal: Dolly the sheep
1. Remove the nucleus from an egg cell (it is now enucleated).
2. Take a diploid nucleus from a mature body cell (Dolly's came from an udder cell) of the sheep to be cloned.
3. Insert this nucleus into the enucleated egg. A small electric shock makes it start dividing.
4. Implant the embryo into a surrogate mother.
The lamb is genetically identical to the sheep that gave the nucleus.
Cloned transgenic animals: an animal genetically modified to make a human protein (for example in its milk) can be cloned, giving a herd that all produce the protein.
2. Take a diploid nucleus from a mature body cell (Dolly's came from an udder cell) of the sheep to be cloned.
3. Insert this nucleus into the enucleated egg. A small electric shock makes it start dividing.
4. Implant the embryo into a surrogate mother.
The lamb is genetically identical to the sheep that gave the nucleus.
Cloned transgenic animals: an animal genetically modified to make a human protein (for example in its milk) can be cloned, giving a herd that all produce the protein.
Dolly's nucleus came from sheep A, the egg from sheep B and she was carried by sheep C. Which sheep is Dolly identical to?
- The genes are in the nucleus.
- The nucleus came from sheep A.
Answer: Sheep A
Micropropagation grows explants in vitro on sterile medium with hormones, producing many identical plants with desirable features. Dolly was made by putting a diploid nucleus from a mature cell into an enucleated egg. Cloned transgenic animals can produce human proteins.
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