Sheep Cloning Ppt

8/3/2019 Sheep Cloning Ppt

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ajay mandal



The term cloning describes a number of differentprocesses that can be used to produce genetically identical copies of a biological entity.

The copied material, which has the same geneticmakeup as the original, is referred to as a clone.



Natural cloning

Artificial cloning

Natural cloning: Yes. In nature, some plants and single-celled

organisms, such as bacteria, produce genetically identical offspring through a process called asexual

reproduction. In asexual reproduction, a new individual is generated

from a copy of a single cell from the parent organism.

http://www.genome.gov/Glossary/?id=15




Natural clones, also known as identical twins,occur in humans and other mammals. These twinsare produced when a fertilized egg splits, creating

two or more embryos that carry almostidentical DNA .(embryo cloning)

Identical twins have nearly the same geneticmakeup as each other, but they are genetically

different from either parent.





There are three different types of artificial cloning: Gene cloning Reproductive cloning Therapeutic cloning

Gene cloning produces copies of genes or segments of DNA.

Reproductive cloning produces copies of whole

animals. Therapeutic cloning produces embryonic stem cells for

experiments aimed at creating tissues to replaceinjured or diseased tissues.



Therapeutic cloning produces embryonic stemcells for experiments aimed at creating tissues toreplace injured or diseased tissues.

Gene cloning, also known as DNA cloning, is a very different process from reproductive andtherapeutic cloning. Reproductive and therapeutic

cloning share many of the same techniques, butare done for different purposes



Roslin cloning technique Honolulu Cloning Technique

Roslin method

The cloning of Dolly has been the most important event in

cloning history.It was not known that an adult nucleus wasstill able to produce a completely new animal.

The discovery by Ian Wilmut and Keith Cambell of amethod with which to synchronize the cell cycles of the

donor cell and the egg cell. Without synchronized cell cycles, the nucleus would not

be in the correct state for the embryo to accept it. Somehowthe donor cell had to be forced into the Gap Zero, or G0 cell

stage, or the dormant cell stage.





• A donor cell was taken from Finn Dorsetand then starved in a mixture which hadonly enough nutrients to keep the cell alive.

• This caused the cell to begin shutting downall active genes and enter the G0 stage. Thecell is said to be quiescent

A quiescent cell has left the cell cycle, ithas stopped dividing. Quiescent cells mightre-enter the cell cycle at some later time, orthey might not. It depends on the type of cell.

Sur rogatemother anddolly



Here the udder

cell is stopped

in Go phase by

growing in

nutrient low

media and

made it

quiescent

cell cyclecontrol





If the embryo survives, it is allowed to grow for aboutsix days, incubating in a sheep's oviduct.

It has been found that cells placed in oviducts early intheir development are much more likely to survivethan those incubated in the lab.

Finally, the embryo is placed into the uterus of asurrogate mother ewe. That ewe then carries the clone

until it is ready to give birth. Assuming nothing goes wrong, an exact copy of the donor animal is born



This newborn sheep has all of the same characteristicsof a normal newborn sheep.

It has yet to be seen if any adverse effects, such as ahigher risk of cancer or other genetic diseases thatoccur with the gradual damage to DNA over time, arepresent in Dolly or other animals cloned with thismethod.





It turns out that her telomeres are only 80% as long asthose in a normal one-year-old sheep.

The examination of DNA from Dolly's cells revealed thather telomeres were abnormally short.

It is known that telomeres are sequences located at the endof each chromosome. These sequences protect DNA fromdegradation by exonucleases. In fact, telomeres areconstantly degraded and restored.



The balance becomes negative as the cells age,

leading to a degradation of chromosomes and to cell deathafter about 50 multiplications.

Dolly's telomeres were short but this was also the case forthe donor cell line, which was derived from an old sheepand was cultured over a long period of time.

Although her nuclear genome came from the Finn Dorsetewe, her mitochondria came from cytoplasm of the

Scottish Blackface ewe. Mitochondria carry their owngenome and so with respect to the genes in mitochondrialDNA , she is not a clone of the Finn Dorset parent.

http://home.comcast.net/~john.kimball1/BiologyPages/E/Endosymbiosis.html






This technological invention is a proven method of producing live, healthy, cloned male or female offspringfrom the fibroblast cells of adult animals. The resultant

viable offspring are true clones of the adult animal that

provided the somatic cells used. This technology comprises two major steps:

Inserting the nucleus of the somatic cell into the cytoplasmof an enucleated oocyte without activating the oocyte to

continue development. Facilitating embryonic development of the reconstituted

oocyte to produce a live offspring.



This animal cloning technique offers the followingfeatures:

Donor cells from a post-natal animal may be obtainedeither from an in vivo source or from a cultured cell line.

Microinjection using a piezo electric micromanipulatorenables a donor nucleus to be harvested and injected usinga single needle. This is a major improvement over the cellfusion method.

Because the removal and subsequent injection of a donornucleus are performed as separate steps, this techniqueallows the harvested nucleic material to be modified prior

to microinjection or mixed with reagents before, during orafter combination with the enucleated oocyte.

These methods are applicable to the cloning of all animals,including amphibians, fish, birds and mammals.



Gene cloning is a carefully regulated technique that islargely accepted today and used routinely in many labs worldwide. However, both reproductive and therapeuticcloning raise important ethical issues, especially as relatedto the potential use of these techniques in humans.

Reproductive cloning would present the potential of creating a human that is genetically identical to anotherperson who has previously existed or who still exists.

This may conflict with long-standing religious and societal

values about human dignity. However, some argue thatreproductive cloning could help sterile couples fulfill theirdream of parenthood.



Others see human cloning as a way to avoid passingon a deleterious gene that runs in the family withouthaving to undergo embryo screening or embryoselection.

Therapeutic cloning, while offering the potential fortreating humans suffering from disease or injury, would require the destruction of human embryos inthe test tube.

Consequently, opponents argue that using thistechnique to collect embryonic stem cells is wrong,regardless of whether such cells are used to benefitsick or injured people.



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Sheep Cloning Ppt