The Manner and Spirit of This Inquiry The question of whether or not to proceed with human cloning-for-biomedical-research is a morally serious and difficult one. On the one hand, there is the promise that such research could lead to important knowledge of human embryological development and gene action, especially in cases in which there are genetic abnormalities that lead to disease. On the other hand, there are the morally relevant facts that this research involves the deliberate production, use, and ultimate destruction of cloned human embryos, and that the cloned embryos produced for research are no different from cloned embryos that could be used in attempts to produce cloned children. Complicating the moral assessment are questions about the likelihood that this research will deliver its promised benefits and about the possibility of equally promising, yet morally less problematic, approaches to the same scientific and medical goals.
Detailed descriptions of methods used in animal cloning and biotechnology are provided in the report Animal Biotechnology: In addition, the committee was charged with evaluating methods to detect potential, unintended, adverse health effects of foods derived from cloned animals. Applications of biotechnology to animal agriculture include improving milk production and composition; increasing growth rate of meat animals; improving productive efficiency, or gain-to-feed ratios, and carcass composition; increasing disease resistance; enhancing reproductive performance; increasing prolificacy; and altering cell and tissue characteristics for biomedical research and manufacturing.
Continued development of new biotechnologies also will allow farm animals to serve as sources of both biopharmaceuticals for human medicine and organs for transplantation. One such example is recombinant-derived bovine somatotropin bST. Commercial use in the United States began in early and has increased to the point that about one-half of all U.
It is, however, important to distinguish the use of bST from other biotechnologies, such as transgenic or cloned animals. Application of recombinant bST is a biotechnology in which a recombinant-derived protein is administered by injection to the recipient animal without changing the animal's genetic composition or genome.
The application of genomics—the study of how the genes in deoxyribonucleic acid DNA are organized and expressed—and bioinformatics in animal agriculture will provide new genetic markers for improved selection for desired traits in all livestock species. Transgenic biology provides a means of altering animal genomes to achieve desired production and health outcomes of commercial value and societal importance.
For example, genetic modification of animals may lead to technologies that reduce the major losses that occur during the first months of embryogenesis. Biotechnology also offers potential to animal agriculture as a means to reduce nutrients and odors from manure and volume of manure produced, resulting in animals that are more environmentally friendly CAST, The advent of techniques to propagate animals by nuclear transfer, also known as cloning, potentially offers many important applications to animal agriculture, including reproducing highly desired elite sires and dams.
Animals selected for cloning will be of great value because of their increased genetic merit for increased food production, disease resistance, and reproductive efficiency, or will be valued because they have been genetically modified to produce organs for transplantation or products with biomedical application.
Before entering the marketplace, new agricultural biotechnologies are evaluated rigorously by the appropriate federal regulatory agencies to ensure efficacy, consumer safety, and animal health and well-being. The development of technologies to clone animals used for food production has raised the question of whether there are unintended compositional changes in food derived from these animals that may, in turn, result in unintended health effects.
CLONING Cloninga term originally used primarily in horticulture to describe asexually produced progeny, means to make a copy of an individual organism, or in cellular and molecular biology, groups of identical cells and replicas of DNA and other molecules.
For example, monozygotic twins are clones. Although clone is descriptive for multiple approaches for cloning animals, in this report clone is used as a descriptor for somatic cell nuclear transfer.
Animal cloning during the late s resulted from the transfer of nuclei from blastomeres of early cleavage-stage embryos into enucleated oocytes, and cloning of livestock and laboratory animals has resulted from transferring a nucleus from a somatic cell into an oocyte from which the nucleus has been removed Westhusin et al.
Somatic cell nuclear transfer can also be used to produce undifferentiated embryonic stem cells, which are matched to the recipient for research and therapy that is independent of the reproductive cloning of animals.
Cloning by nuclear transfer from embryonic blastomeres Willadsen, ; Willadsen and Polge, or from a differentiated cell of an adult Kuhholzer and Prather, ; Polejaeva et al.
The offspring will be identical to their siblings and to the original donor animal in terms of their nuclear DNA, but will differ in their mitochondrial genes; variances in the manner nuclear genes are expressed are also possible. Epigenetic Change in the Genome Epigenetics is the study of factors that influence behavior of a cell without directly affecting its DNA or other genetic components.
The epigenetic view of differentiation is that cells undergo differentiation events that depend on correct temporal and spatial repression, derepression, or activation of genes affecting the fate of cells, tissues, organs, and ultimately, organisms.
Thus epigenetic changes in an organism are normal and result in alterations in gene expression. For example, epigenetic transformation of a normal cell to a tumor cell can occur without mutation of any gene. Effects of Cloning Santos and colleagues have reviewed current thinking on epigenetic marking that correlates with developmental potential of cloned bovine preimplantation embryos.
They indicate that reprogramming of DNA methylation affects the entire genome of mammalian embryos both during phase I germline development when DNA methylation imprints are eliminated and during phase II preimplantation development of mammalian embryos.
Phase II DNA reprogramming is initiated upon fertilization of the oocyte for remodeling of chromatin in the male pronucleus and selective demethylation of its DNA, while subsequent DNA demethylation in early cleavage stage embryos is passive.
At the blastocyst stage, de novo methylation is lineage-specific as the inner cell mass, or embryonic disc, becomes highly methylated and trophectoderm becomes hypomethylated. These epigenetic reprogramming events appear to be deficient in cloned embryos that have abnormal patterns of DNA methylation and gene expression.
Cloning by nuclear transfer using present methods is very inefficient. This is likely due to the limited ability of oocyte cytoplasm to reprogram somatic cell nuclear DNA, whereas it readily reprograms sperm cell nuclear DNA Wilmut et al.
Consequently, there are very high rates of embryonic, fetal, perinatal, and neonatal deaths, as well as birth of offspring with various abnormalities. These losses are assumed to result from inappropriate expression of genes during various stages of development, with less than 4 percent of embryos reconstructed using adult or fetal somatic cell nuclei being born as live young.
A very high percentage of fertilized eggs that develop and survive beyond the first 30 to 60 days of gestation in sheep and cattle have abnormal placental morphology, such as reduced vascularity and abnormal or few cotyledons; abnormal placental functions, such as hydroallantois and hydroamnios; and abnormal fetal development, such as enlarged liver, hydrops fetalis, dermal hemorrhaging, and swollen brain.
Neonates also often experience respiratory distress and cardiovascular abnormalities De Sousa et al. In addition, there is evidence for abnormalities of the immune system, brain, and digestive system of cloned animals.
Mice cloned from cumulus cells become obese, but this trait is not heritable after sexual reproduction, which is direct evidence that obesity in the clones result from epigenetic events Tamashiro et al. Wilmut and colleagues have reported that a number of cellular factors influence the outcome of cloned offspring.
First, normal development depends on the embryo having normal ploidy, which is achieved by coordinating stage of cell cycle of the recipient oocyte and donor nucleus.acceptance of reproductive cloning and human genetic manipulation.
It is possible to support stem cell research and still oppose research involving therapeutic cloning. In addition to analyzing the direct ethical, legal and social implications of the Human Genome Project (HGP), the National Human Genome Research Institute (NHGRI) funds examinations of issues that are related because they involve manipulation of human genetic material or information.
Gene cloning is the most common type of cloning done by researchers at the National Human Genome Research Institute (NHGRI). NHGRI researchers have not cloned any mammals and NHGRI does not clone humans.
Human Genetic Engineering Fact Sheet Watch CRG Board Chair Sheldon Krimsky on the future of genetic engineering before a live studio audience Should we prohibit genetically engineered children?(PBS) Or listen on NPR. CRG's Position on Cloning The CRG strongly opposes human reproductive cloning.
D-4 genotypes to avoid overloading the human gene pool with deleterious genes and thereby placing the survival of the human species at risk.
Prominent theologians engaged in these initial discussions of genetic manipulation and. Four panels addressed the specific scientific, religious, ethical, and legal implications of human reproductive cloning and stem cell research.
This document gives a brief summary of the issues as they were raised by the four panels.