Cloning

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)


• 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

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

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

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

Cloning

Education

Transcript of Cloning