Cloning Animals

Creating genetically identical offspring

Embryo splitting- artificial identical twins

In this simple form a ram with desirable genes is selected (e.g. long coat)The ewe with desirable characteristics is also chosen the egg and sperm are fertilized in vitroThe zygote is allowed to grow in vitro to 16 cells then split. The cell bundle can be split in two or more and implanted into one or several surrogate mothers.

Artificial cloning of animals (nuclear transfer)

The most popular method involves removing the nucleus from the body cell of your animal to be cloned (usually a mammary cell)Take an egg (ovum) of the same species and remove its nucleus (enucleation)

Artificial cloning of mammals

Insert the genetic information (nucleus) from the body cell into the ovum (electro fusion)Implant the ovum into the oviduct of a surrogate female female to cultureImplant the early embryo into a final surrogate motherAwait birth!

Nuclear transfer method - summary

In this the mammary cells are removed from the desired clone sheepAn egg cell (ovum) from another sheep is enucleatedThe mammary nucleus is implanted into the enucleated egg by electro fusionThis egg is ‘cultured’ in the oviduct of another sheep and finally implanted into the uterus of a fourthIt took 277 attempts!

Nuclear transfer - using an ovum/oocyte.

The oocyte had to be enucleated to remove the unwanted genetic material so only the ‘clone’ DNA would be replicated.The oocyte is large with extra nutrients to enable development.It is specialized for reproduction and will begin to divide spontaneously and implant in the uterus.These totipotent cells have the capability of turning on any gene in the genome.

                                    

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Embryo splittingThis is a simpler method.Sperm and egg are selected.They are fertilized in vitroThe zygote divides to a 16 cell embryo,This is split into four or more, These are implanted into 4 surrogate mothers.

Advantages of cloning animals

There are hundreds of cloned animals round the world.Desirable trait beasts (e.g. leanest for meat good milkers) can be copied exactly with no variationEndangered species can be copied.Animals altered for pharmaceutical purposes can be copied.

Use of cloning to treat disease- Neutrophils in the lungs

During a lung infection it is necessary for white blood cells to get into the lungsThis is achieved by the white blood cells producing elastase to digest little holes in the alveoli

Alpha Anti-trypsinAAT is manufactured by the walls of the alveoli to prevent the further breakdown of the elastin by the White Blood Cells.In humans incapable of producing AAT a series of lung infections can seriously weaken the lungs

Loss of elasticityWhile inspiration is unaffected, expiration and so removal of carbon dioxide becomes less efficientThis can lead to hyperventilation and feelings of suffocationIt is similar in nature to emphysema

How to treat the problemAdministering Alpha Anti-trypsin is an effective treatment to prevent this elastin breakdownCurrently the main source of AAT is from blood donations

Engineering AAT production in milkTracey the sheep.

An egg from a ewe was fertilized with a sperm from a ram in vitro. A plasmid containing the human gene for AAT production was then inserted into the egg using a micropipetteThe zygote was transferred back to the mother’s wombAfter many attempts the world’s first transgenic ewe (Tracey) was born

Tracey (transgenic ewe)

The success of transgenic ewes

Tracey produces 35g of AAT in every litre of milk which is an enormous amount. The genes for making AAT were passed to some of her ewe lambsA mere 2000 ewes like Tracey would produce enough milk to supply all the hospitals in the world.

Disadvantages of cloningDolly the sheep died of lung cancer (the initial report of premature ageing was wrong) It is still unclear whether cloning animals with older genetic material is detrimental to the health of the cloneIt is costly – low success rate expensive technologyA clone flock (genetic uniformity)would soon be wiped out by a disease to which their genetic type was susceptible

Non-reproductive cloningAlso known as therapeutic cloning.Biotechnology has already enabled Biologists to artificially produce simple organs such as bladders to replace those removed due to bladder cancer.Using the individual’s own cells to produce new organs eliminates the problem of rejection.