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CLONINGAn Overview
GROUP MEMBERS• HASSAN TARIQ (2008-EE-180)
Introduction and OverviewCloning in Nature
• ZAIR HUSSAIN (2008-EE-177)History of Cloning
• SAQIB SAEED (2008-EE-168)How scientists clone cells
• UMAIR MAQBOOL (2008-EE-178)Stem cells technologyBenefits of Cloning
Introduction and overview
Introduction• Cloning: Creating copies of living matter• The term clone (from the Greek word klōn,
meaning “twig”) had already been in use since the beginning of the 20th century in reference to plants
• Clones have identical genetic makeup• Abundant in nature• Used by scientists to generate organisms with
valuable traits
Historical Perspective
• Farmers started using it thousands of years ago
• Revolutionized in late 20th Century with the advent of genetic engineering
Cloning in Animals
• To generate animals with desirable traits
• To bolster endangered species
• Maybe in near future, extinct animals can be resurrected
Industrial Perspective
• Production of bacteria which can clean up environmental contamination
• Animals which can produce commercial ingredients e.g. protein
Importance for Humans
• Promises great advances in medicine
• Biomedical scientists plan to create animals with human diseases, so that cures can be experimented safely
CLONING IN NATURE
In Bacteria and Plants
• Originated in nature• Most organisms
reproduce asexually• Unicellular organisms
reproduce by fission, a cloning method
• Plants like strawberries clone by producing runners
In Animals and Mammals
• Some species of fish, shrimps, lizards and frogs produce by parthenogenesis- from Greek word parthenos (“virgin”) and genesis (“birth”)
• Clones in mammals- genetic copies of each other
HISTORY OF CLONING
Initial Efforts• 1800’s- First try of using
undifferentiated cells Hans Dreisch separated a sea urchin
embryo when it was just two cells Both cells grew to adults
• Early 1900’s- Hans Spemann extended Dreisch’s work to salamanders Determined that nucleus from
embryo cell could direct the development of a complete organism
Published his results in 1938 Proposed a “fantastical” experiment
Early Frog Experiments
• 1952- Spemann’s idea realized by Robert Briggs and Thomas King Used cell nuclear transfer to
insert DNA from a frog embryo cell into an enucleated frog egg
Resulting embryo grew into an adult
Early experiments using cell nuclear transfer were successful only when donor DNA was taken from an embryonic cell
Early Frog Experiments (Gurdon’s Method)
• 1962- John Gurdon began cloning experiments using non-embryonic cells Cells from intestinal lining of tadpoles Exposed a frog egg to ultraviolet light, which
destroyed its nucleus Removed the nucleus from the tadpole intestinal
cell and implanted it in the enucleated egg Egg grew into a tadpole that was genetically
identical to the DNA-donating tadpole
Impact of Gurdon’s Research
• Gurdon’s experiments captured the attention of the scientific community
• Tools and techniques he developed for nuclear transfer are still used today
• 1963- J. B. S. Haldane, in describing Gurdon’s results, became one of the first to use the word clone in reference to animals
Glitches of Gurdon’s Method
• Tadpoles cloned in Gurdon’s experiments never survived to adulthood
• Scientists now believe that cells used may not have been differentiated cells
Mammal Cloning (Initial Efforts)
• Scientists turned their attention to cloning mammals
• Proved even more complex than earlier cloning experiments on invertebrates and amphibians
• 1977- Karl Illmensee reported cloning mice from cells derived from early embryos Illmensee’s findings were largely discredited because he
used questionable laboratory techniques
• Agricultural researchers tried to clone cattle using somatic cell nuclear transfer, but failed
Mammal Cloning(Breakthrough)
• 1984- First mammal cloned Danish biologist Steen Willadsen Working at Cambridge University in England
• Used nuclear transfer with DNA from early embryonic cells
• Two years later, a team of researchers at the University of Wisconsin cloned a cow through a similar approach
Mammal Cloning (Further Developments)
• 1990’s- Cloning techniques advanced rapidly• 1995- Two lambs cloned
By Keith Campbell and Ian Wilmut at the Roslin Institute
From embryonic cells; named Megan and Morag Scientists were able to keep the embryonic cells alive
in culture for some time before beginning the cloning procedure
• Enabled scientists to modify an embryonic cell’s genes in culture before cloning
• Genetically modified livestock can be produced
Megan and Morag
BLASTOMERE SEPARATION
BLASTOCYST DIVISION
SOMATIC CELL NUCLEAR TRANSFER
HOW SCIENTISTS CLONE CELLS…
Up till 1950’s
• Initial Efforts- Letting a single cell divide in a laboratory dish by ‘mitosis’
• Complex Techniques- Using animal embryos
• 1950’s- Using cells that haven’t been differentiated yet (totipotent)
HOW SCIENTISTS CLONE CELLS…
• BLASTOMERE SEPARATION
• BLASTOCYST DIVISION
• SOMATIC CELL NUCLEAR TRANSFER
Blastomere Separation
• Fertilize an egg cell with a sperm cell in a laboratory dish till embryo is of about 4 cells
• Outer coating of embryo removed• Placed in a solution to separate individual cells
(Blastomeres)• Each blastomere cultured separately• Embryos implanted into surrogate mothers
HOW SCIENTISTS CLONE CELLS…
• BLASTOMERE SEPARATION
• BLASTOCYST DIVISION
• SOMATIC CELL NUCLEAR TRANSFER
Blastocyst Division
• Fertilized cell allowed to divide till mass is 30-150 cells (Blastocyst)
• Split Blastocyte into two
• Each half implanted in a surrogate mother
• Creation of identical twins
HOW SCIENTISTS CLONE CELLS…
• BLASTOMERE SEPARATION
• BLASTOCYST DIVISION
• SOMATIC CELL NUCLEAR TRANSFER
Somatic Cell Nuclear Transfer (Overview)
• Use cells of only ONE parent• Somatic Cell (any body cell EXCEPT an egg or a
sperm)• Enucleated Egg Cell (egg with its nucleus
removed)• Merge both cells via fusion• Only applicable on immature cells (either
embryonic, or of young animals)
Somatic Cell Nuclear Transfer (Breakthrough- Birth of Dolly)
• In 1996, by improved somatic cell nuclear transfer method
• Donor cell made quiescent (less active)• Transfer of genetic material from udder cell to
an enucleated cell (from a second sheep)• Resulting embryo was implanted into the
uterus of a third sheep• Now donor cells can be taken from adult
animals
Egg Donor
Genetic Donor
Enucleated Cell
Embryo Development
Embryo Implantation
Birth
Somatic Cell Nuclear Transfer (Glitches)
• All genes are NOT in nucleus, so all genes of the clone are NOT those of the donor
• Since every organism is influenced by, both genes and the environment, so the clone’s life will be different from that of the parent
STEM CELLS AND CLONING
Basics• At Blastocyte stage,
embryonic cells can divide into ALL types of cells needed by the organism
• Scientists separate these cells and coax them to divide under special conditions (so that they can form any cell type)
• Humans maintain some stem cells in some tissue of body till death. But with aging, they lose ability to transform into different cell types (cells from bone marrow is exception)
Benefits• Can be used to cure diseases
• If a patient receives stem cells cloned containing his own genetic material, then his/ her immune system would not reject them as foreign material
• Research going on to find cure for Parkinson’s, paralysis, damaged heart muscles, arthritis and diabetes mellitus
Results
• Still in experimental stage
• First clinical trial of curing patients suffering from Parkinson’s produced mixed results Patients over 60 years old reported no
improvement Younger patients reported some improvement,
but 15% of them sport irreversible side effects, like uncontrollable twitching
Risks• If some error occurred during cloning, then all
resulting cells will have same error• However, in 2002, scientists at Rutgers
University found comparatively fewer genetic mutations
• Risk of transferring disease via stem cells Typically, scientists culture human stem cells with
mouse cells Mouse cells have some unknown nutrient that
keeps human stem cells alive So human cells can easily be infected by mouse cells
Benefits of Cloning
Benefits of Animal Cloning• In Agriculture
Cloned cattle could produce higher yield of milk & meat
Can also produce drugs at commercial level
• In Laboratory Create animals with human diseases Can test cures on them safely
Cloning Endangered & Extinct Species
• 2001- Gaur (endangered ox of South-East Asia) cloned successfully
• Plan to revive extinct species by cloning Cells of last Spanish ibex
(mountain goat) preserved for the same purpose
• Prerequisites Cell with intact nucleus Surrogate mother needed
with similar genetic makeup, to implant the embryo
Can Humans Be Cloned…….?
• Impossible up till now
• In human embryo, number of cells become twice after every 24 hours Not achieved yet in laboratory
• Not enough funding due to its controversial nature
Controversies
• People do not consider plant cloning as cloning: Main opposition is against animal cloning
• Arguments: Man should not play GodWill increase social gaps, as babies with special
traits, like beauty, athleticism, or intelligence can be created