Cloning can it be done

Other consequences include premature aging and problems with the immune system. Another potential problem centers on the relative age of the cloned cell's chromosomes. As cells go through their normal rounds of division, the tips of the chromosomes, called telomeres, shrink. Over time, the telomeres become so short that the cell can no longer divide and, consequently, the cell dies.

This is part of the natural aging process that seems to happen in all cell types. As a consequence, clones created from a cell taken from an adult might have chromosomes that are already shorter than normal, which may condemn the clones' cells to a shorter life span. Indeed, Dolly, who was cloned from the cell of a 6-year-old sheep, had chromosomes that were shorter than those of other sheep her age.

Dolly died when she was six years old, about half the average sheep's year lifespan. Therapeutic cloning involves creating a cloned embryo for the sole purpose of producing embryonic stem cells with the same DNA as the donor cell. These stem cells can be used in experiments aimed at understanding disease and developing new treatments for disease.

To date, there is no evidence that human embryos have been produced for therapeutic cloning. The richest source of embryonic stem cells is tissue formed during the first five days after the egg has started to divide.

At this stage of development, called the blastocyst, the embryo consists of a cluster of about cells that can become any cell type. Stem cells are harvested from cloned embryos at this stage of development, resulting in destruction of the embryo while it is still in the test tube. Researchers hope to use embryonic stem cells, which have the unique ability to generate virtually all types of cells in an organism, to grow healthy tissues in the laboratory that can be used replace injured or diseased tissues.

In addition, it may be possible to learn more about the molecular causes of disease by studying embryonic stem cell lines from cloned embryos derived from the cells of animals or humans with different diseases. Finally, differentiated tissues derived from ES cells are excellent tools to test new therapeutic drugs. Many researchers think it is worthwhile to explore the use of embryonic stem cells as a path for treating human diseases. However, some experts are concerned about the striking similarities between stem cells and cancer cells.

Both cell types have the ability to proliferate indefinitely and some studies show that after 60 cycles of cell division, stem cells can accumulate mutations that could lead to cancer.

Therefore, the relationship between stem cells and cancer cells needs to be more clearly understood if stem cells are to be used to treat human disease. Gene cloning is a carefully regulated technique that is largely accepted today and used routinely in many labs worldwide. However, both reproductive and therapeutic cloning raise important ethical issues, especially as related to the potential use of these techniques in humans. Reproductive cloning would present the potential of creating a human that is genetically identical to another person who has previously existed or who still exists.

This may conflict with long-standing religious and societal values about human dignity, possibly infringing upon principles of individual freedom, identity and autonomy. However, some argue that reproductive cloning could help sterile couples fulfill their dream of parenthood. Others see human cloning as a way to avoid passing on a deleterious gene that runs in the family without having to undergo embryo screening or embryo selection.

Therapeutic cloning, while offering the potential for treating humans suffering from disease or injury, would require the destruction of human embryos in the test tube. Consequently, opponents argue that using this technique to collect embryonic stem cells is wrong, regardless of whether such cells are used to benefit sick or injured people. Cloning Fact Sheet. Do clones ever occur naturally? What are the types of artificial cloning?

How are genes cloned? How are animals cloned? What animals have been cloned? Have humans been cloned? Do cloned animals always look identical? What are the potential applications of cloned animals? What are the potential drawbacks of cloning animals? What is therapeutic cloning? Cloned rabbits produced by nuclear transfer from adult somatic cells. Nature Biotechnol. CAS Google Scholar. King, T. Embryo development and establishment of pregnancy after embryo transfer in pigs: coping with limitations in the availability of viable embryos.

Reproduction , — De Sousa, P. Somatic cell nuclear transfer in the pig: control of pronuclear formation and integration with improved methods for activation and maintenance of pregnancy.

Woods, G. A mule cloned from foetal cells by nuclear transfer. Science , Zhou, Q. Generation of fertile cloned rats using controlled timing of oocyte activation. Science 25 September doi This was the first report of successful cloning of the rat by controlling oocyte activation. Hayes, E. Nuclear transfer of adult and genetically modified fetal cells of the rat. Genomics 5 , — Young, L. Large offspring syndrome in cattle and sheep.

Reik, W. Imprinting in clusters: lessons from Beckwith—Wiedemann syndrome. Trends Genet. DeBaun, M. Hill, J. Evidence for placental abnormality as the major cause of mortality in first-trimester somatic cell cloned bovine fetuses.

Evaluation of gestational deficiencies in cloned sheep fetuses and placentae. References 15 and 16 document placental abnormalities in cloned sheep and cattle. Tanaka, S.

Placentomegaly in cloned mouse concepti caused by expansion of the spongiotrophoblast layer. Booth, P. Numerical chromosome errors in day 7 somatic nuclear transfer bovine blastocysts. Tamashiro, K. Cloned mice have an obese phenotype not transmitted to their offspring. Nature Med. This paper shows that the increased body weight of cloned female mice reflects an increase in body fat as well as larger body size; this obese phenotype is not transmitted to offspring.

Santos, F. Epigenetic marking correlates with developmental potential in cloned bovine preimplantation embryos. This paper reports histone and DNA hypermethylation in cloned bovine embryos and provides further evidence that the epigenotype of cloned embryos depends on the donor-cell type.

Google Scholar. Li, E. Chromatin modification and epigenetic reprogramming in mammalian development. Nature Rev. Selig, S. Regulation of mouse satellite DNA-replication time. EMBO J. Jaenisch, R. DNA methylation and imprinting: why bother? Barlow, D. Methylation and imprinting — from host defense to gene-regulation. Role for DNA methylation in genomic imprinting.

Jones, P. Relationships between chromatin organization and DNA methylation in determining gene expression. Seminars Cancer Biol. Shemer, R. Dynamic methylation adjustment and counting as part of imprinting mechanisms. Natl Acad. USA 93 , — Mayer, W. Embryogenesis — demethylation of the zygotic paternal genome.

Oswald, J. Active demethylation of the paternal genome in the mouse zygote. Rougier, N. Chromosome methylation patterns during mammalian preimplantation development. Genes Dev. Monk, M. Temporal and regional changes in DNA methylation in the embryonic, extraembryonic and germ-cell lineages during mouse embryo development.

Development 99 , — Dean, W. Conservation of methylation reprogramming in mammalian development: aberrant reprogramming in cloned embryos. USA 98 , — This paper shows that epigenetic reprogramming occurs aberrantly in most cloned embryos.

Somatic cell nuclear transfer. Kang, Y. Aberrant methylation of donor genome in cloned bovine embryos. Nature Genet.

These results show highly aberrant methylation patterns in various genomic regions of cloned embryos. Bourc'his, D. Delayed and incomplete reprogramming of chromosome methylation patterns in bovine cloned embryos. Limited demethylation leaves mosaic-type methylation states in cloned bovine pre-implantation embryos. Chung, Y. Abnormal regulation of DNA methyltransferase expression in cloned mouse embryos.

Typical demethylation events in cloned pig embryos — clues on species-specific differences in epigenetic reprogramming of a cloned donor genome. Mann, M. Disruption of imprinted gene methylation and expression in cloned preimplantation stage mouse embryos.

This study shows that epigenetic errors can arise early in clone development. Gametic imprinting in mammals. Chavatte-Palmer, P. Clinical, hormonal, and hematologic characteristics of bovine calves derived from nuclei from somatic cells.

Rhind, S. Cloned lambs: lessons from pathology. Improving the safety of embryo technologies: possible role of genomic imprinting. Theriogenology 53 , — Kruip, T. In vitro produced and cloned embryos: effects on pregnancy, parturition and offspring. Theriogenology 47 , 43—52 Epigenetic change in IGF2R is associated with fetal overgrowth after sheep embryo culture. This paper shows reduced fetal methylation and expression of ovine IGF2R in association with large offspring syndrome.

Humpherys, D. Epigenetic instability in ES cells and cloned mice. Science , 95—97 This study reports epigenetic abnormalities in both ES cells and clones, with the further implication that even apparently normal cloned animals might have subtle abnormalities in gene expression.

Scientists can turn them into nerve cells to fix a damaged spinal cord or insulin-making cells to treat diabetes. The cloning of animals has been used in a number of different applications.

Animals have been cloned to have gene mutations that help scientists study diseases that develop in the animals. Livestock like cows and pigs have been cloned to produce more milk or meat. In , a cat named CC was the first pet to be created through cloning. Cloning might one day bring back extinct species like the woolly mammoth or giant panda. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

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Mendel bred peas and noticed he could cross-pollinate them in certain ways to get green or yellow seeds. Today, the field of genetics is breaking new ground searching for new ways to treat disease or develop crops more resistant to insects or drought. Empower your students to learn about genetics with this collection of resources. Biotechnology is the use of living systems and organisms to create new technologies. On the simpler end of the spectrum, baking bread with yeast is an example of this interdisciplinary science.

On the more complex side, genetic engineering, biochemistry, and molecular biology are pushing boundaries in an effort to treat illnesses, develop new biofuels, and grow plants more efficiently to feed more people.