Download - Cloning
Cloning
Dr. Abdelsalam Talafha, DVM
Diplomate, American College of Theriogenologists
Cloning
• Production of genetically identical individuals that have identical nuclear DNA
Cloning Technologies
1. Recombinant DNA technology• DNA cloning• Molecular cloning• Gene cloning
2. Reproductive cloning
3. Therapeutic cloning• Embryo cloning
DNA Cloning
• Transfer of a DNA fragment of interest from one organism to a self-replicating genetic element such as a bacterial plasmid
• Plasmids• Self-replicating extra-chromosomal circular
DNA molecules, distinct from normal bacterial genome
DNA Cloning - Uses
• Gene therapy• Genetic engineering of organisms• Genome sequencing
Reproductive Cloning
• A technology used to generate an animal that has same nuclear DNA as another currently or previously existing animal
• Dolly• How Is Reproductive Cloning Done?
• Somatic cell nuclear transfer (SCNT)
SCNT
• Starts with removal of polar body and chromosomes from an oocyte • Enucleated oocyte
• Donor cell then inserted into perivitelline space of enucleated oocyte
SCNT
• Oocyte and donor cell are fused and activated by an electric pulse to begin cell division
• Developed embryos transferred to surrogate females
• Birth of an individual
SCNT
• Sources of somatic cells• Cell from individual• Cells grown in culture• Frozen tissue
Therapeutic Cloning
• Production of human embryos for use in research
• Goal • To harvest stem cells that can be used to
study human development and to treat disease
Therapeutic Cloning
• Stem cells • Cells have ability to divide and give rise to
both specialized cells and more stem cells• Derived from
• Adults • Preimplantation embryos (Embryonic stem
cells)
Stem Cells
• Replacement cells to treat • Heart disease• Alzheimer's• Cancer• Diabetes• Parkinson's disease• Spinal cord injury
SCNT- Potential Biotechnological Applications
• Harvesting donor cells from transgenic animal• Genetic modification of cultured donor cells
prior to nuclear transfer• Producing genetically modified cloned
offspring
Genetically Modified Cloned Offspring
• Biotechnological applications • Production of pharmaceuticals• Xenotransplantation• Study and eradication of human disease• Improvement of livestock
Production Of Pharmaceuticals
• Gene expressing human coagulation factor IX introduced into ovine fetal fibroblasts
• linked to another gene with a high level of expression in mammary gland
• Protein expressed in milk
Production Of Pharmaceuticals
• Insulin for diabetes• Interferon for viral infections• Tissue plasminogen activator (which
dissolves blood clots)
Xenotransplantation
• Aim:• To develop animals whose organs will not
cause an immunological response and destroy transplanted tissue when transferred to humans
Xenotransplantation
• Pig organs• Hearts, lungs, kidneys, liver • Neural tissue for Parkinson's • Islets cells for diabetes patients
Study Human Disease
• Sheep model to investigate human cystic fibrosis
• Cloned sheep used for drug testing and to evaluate new therapies
Improvement Of Livestock
• Cloning animal with excellent traits• Production of a large number of clones from
high quality animals • Allow overall genetic improvement of herd
• Repopulate endangered animals
Animal Cloning
• Sheep, cattle, goats, pigs, and mice• Cloning efforts in rabbits, rats, cats, dogs,
and horses are ongoing
Risks Of Cloning
• Reproductive cloning expensive and highly inefficient
• > 90% of cloning attempts fail to produce viable offspring
Risks Of Cloning
• High rate of fetal loss during pregnancy • Compromised immune function • Higher rates of infection• Tumor growth• Early neonatal death • Abnormally large at birth• Die mysteriously
Risks Of Cloning
• Cloned fetuses have abnormalities• Abnormal placentation• Pregnancy toxemia• Hydroallantois
Should Humans Be Cloned?
• Due to• Inefficiency of animal cloning • Lack of understanding about reproductive
cloning• Risks of cloning
Should Humans Be Cloned?
• Unethical to attempt to clone humans• Same problems would be expected in
human cloning• We do not know how cloning could impact
mental development
Should Humans Be Cloned?
• High risk to health of fetus or infant and mother
• Psychological risks for mother as a result of • Late spontaneous abortions • Birth of a stillborn child • Birth of a child with severe health problems