Genetic Copies Research Articles

Inter-institutional laboratory standardization for SARS-CoV-2 surveillance through wastewater-based epidemiology applied to Mexico City

ObjectivesWastewater-based surveillance applied to SARS-CoV-2 viral load quantification for COVID-19 has become one of the most relevant complementary tools in epidemiologic prevention programs worldwide. However, this valuable decision-making tool still requires fine-tuning to produce comparable results between laboratories, especially when applied to the surveillance of megacities. MethodsSix laboratories across Mexico and one from the United States executed an interlaboratory study to set up a singular standardized protocol considering method cost, installed infrastructure, materials available, and supply availability for SARS-CoV-2 quantification from five Mexico City sampling sites across this megacity. ResultsComparable data from processing outcomes in the Mexican laboratories and in the external international laboratory serve as a validating data source. The Bland–Altman comparison showed consistency, with cycle threshold values within ±1.96 SD of SARS-CoV-2 genetic copies for the standard curve quantification, with a mismatch of two laboratories. In addition, MS2 bacteriophage recovery rates varied between 35% and 67% among all participating laboratories. Finally, the efficiency of viral genetic material recovered from all participating laboratories varied between 65% and 93% for the participating laboratories. ConclusionThis work lays the foundation for extensive and continuous wastewater-based surveillance application across independent Mexican laboratories in a time- and resource-effective manner.

Label-Free Detection of Virus-like Particles with Surface-Enhanced Raman Spectroscopy through Analyte Localization and Polymer-Enabled Capture.

Virus detection is highly important; the last several years, since the onset of the SARS-CoV-2 pandemic, have highlighted a weakness in the field: the need for highly specialized and complex methodology for sensitive virus detection, which also manifests as sacrifices in limits of detection made to achieve simple and rapid sensing. Surface-enhanced Raman spectroscopy (SERS) has the potential to fill this gap, and two novel approaches to the development of a detection scheme are presented in this study. First, the physical entrapment of vesicular stomatitis virus (VSV) and additional virus-like particles through substrate design to localize virus analytes into SERS hotspots is explored. Then, the use of nonspecific linear polymers as affinity agents to facilitate polymer-enabled capture of the VSV for SERS detection is studied. Quantitative detection of the VSV is achieved down to 101 genetic copies per milliliter with an R2 of 0.987 using the optimized physical entrapment method. Physical entrapment of two more virus-like particles is demonstrated with electron microscopy, and distinctive SERS fingerprints are shown. This study shows great promise for the further exploration of label-free virus detection methods involving thoughtful substrate design and unconventional affinity agents.

Premeiotic endoreplication is essential for obligate parthenogenesis in geckos.

Obligate parthenogenesis evolved in reptiles convergently several times, mainly through interspecific hybridization. The obligate parthenogenetic complexes typically include both diploid and triploid lineages. Offspring of parthenogenetic hybrids are genetic copies of their mother; however, the cellular mechanism enabling the production of unreduced cells is largely unknown. Here, we show that oocytes go through meiosis in three widespread, or even strongly invasive, obligate parthenogenetic complexes of geckos, namely in diploid and triploid Lepidodactylus lugubris, and triploid Hemiphyllodactylus typus and Heteronotia binoei. In all four lineages, the majority of oocytes enter the pachytene at the original ploidy level, but their chromosomes cannot pair properly and instead form univalents, bivalents and multivalents. Unreduced eggs with clonally inherited genomes are formed from germ cells that had undergone premeiotic endoreplication, in which appropriate segregation is ensured by the formation of bivalents made from copies of identical chromosomes. We conclude that the induction of premeiotic endoreplication in reptiles was independently co-opted at least four times as an essential component of parthenogenetic reproduction and that this mechanism enables the emergence of fertile polyploid lineages within parthenogenetic complexes.

Is a deterministic chaos the way to cancerogenesis?

On the basis of the 2nd law of thermodynamics, the study presents a probable process in which a neoplastic cell passes into the dissipative state on its thermodynamic branch and self-transforms into a neoplastic cell. The self-transformation is promoted by a long-term unstable, highly unbalanced state in which cells that are sensitive to cancerogenesis obtain their own thermodynamic branch, and their self-organization is probably based on a disturbed relationship between entropy and temperature. Self-organization is related to the progressive imbalance. It promotes mistakes during genetic copies formation , spontaneous mutations and, as a result, cancerogenesis. A deterministic chaos is a creative process because it is the only one capable of generating completely new structures, such as neoplasms. Neoplastic cells succeed only when their environment (extracellular matrix – ECM) is damaged due to e.g. senile inflammation or inflammation caused by the neoplasm itself. This is known as the oncogenesis adaptation theory and it explains the evolution of neoplastic cells. The mutation leading to the neoplastic transformation of a cell is sometimes unfavorable or even harmful to the cell by preventing its proper adaptation to surrounding tissues. This can be useful in adaptive therapy of some neoplasms.

Genes & cells: Ancestral humans had more DNA: Genetic cuts and copies show evolutionary kinships

Genes & cells: Ancestral humans had more DNA: Genetic cuts and copies show evolutionary kinships

Integrated quantum dot barcode smartphone optical device for wireless multiplexed diagnosis of infected patients.

Inorganic nanoparticles are ideal precursors for engineering barcodes for rapidly detecting diseases. Despite advances in the chemical design of these barcodes, they have not advanced to clinical use because they lack sensitivity and are not cost-effective due to requirement of a large read-out system. Here we combined recent advances in quantum dot barcode technology with smartphones and isothermal amplification to engineer a simple and low-cost chip-based wireless multiplex diagnostic device. We characterized the analytical performance of this device and demonstrated that the device is capable of detecting down to 1000 viral genetic copies per milliliter, and this enabled the diagnosis of patients infected with HIV or hepatitis B. More importantly, the barcoding enabled us to detect multiple infectious pathogens simultaneously, in a single test, in less than 1 h. This multiplexing capability of the device enables the diagnosis of infections that are difficult to differentiate clinically due to common symptoms such as a fever or rash. The integration of quantum dot barcoding technology with a smartphone reader provides a capacity for global surveillance of infectious diseases and the potential to accelerate knowledge exchange transfer of emerging or exigent disease threats with healthcare and military organizations in real time.

On Clone as Genetic Copy: Critique of a Metaphor

A common feature of scientific and ethical debates is that clones are generally described and understood as “copies” or, more specifically defined, as “genetic copies.” The attempt of this paper is to question this widespread definition. It first argues that the terminology of “clone as copy” can only be understood as a metaphor, and therefore, a clone is not a “genetic copy” in a strict literal sense, but in a figurative one. Second, the copy metaphor has a normative component that is problematic in the context of descriptive science and may support or indicate the ethically relevant phenomenon of objectification of animals. In order to support the argument against the common conception of a clone as a copy, the biotechnological principles of somatic cell nuclear transfer (SCNT) cloning will be examined. On this basis, it will be shown that the metaphor is valid because of similarities between the phenotype, the genotype, or the nuclear DNA sequence of the clone and its progenitor by using three prominent levels of comparison (clone as phenotypical, genotypical, and nuclear copy). Focusing on the process of SCNT, it will be shown that cloning as copying or doubling has to be redefined for scientific purposes because it is neither necessary nor does it fit to the biotechnological principles of cloning. It is more accurate to understand SCNT cloning as a process of splitting rather than of doubling or copying. In the second part, a deconstructivist analysis based on Jacques Derrida’s description in Positions (1981) will reveal the normative potential of the original–copy dichotomy. I will be showing that it includes an asymmetrical power structure between the original (progenitor) and the copy (clone) and that this structure can be reversed or at least considered unstable. Therefore, arguments that build on that metaphor must be reconsidered. Moreover, the analysis reveals that applying a terminology to humans and animals that is commonly used for things becomes the language of objectification. Two selected examples, fungibility and violability, based on Martha Nussbaum’s notion of objectification will support the thesis of objectification, display its normative consequences, and put the clone as a copy metaphor in a broader range of ethically questionable research tendencies.

Assessment of Disease Intensity and Evaluation of Enset Clones against Bacterial Wilt (<I>Xanthomonas campestris pv. Musacearum</I>) in Tikur Inchini and Jibat Districts of West Shewa, Ethiopia

Enset ( Ensete ventricosum Welw. Cheesman) is an important staple food crops in Ethiopia, which is widely cultivated in Southern and South western parts of the country. However, its production has been threatened by one of the devastating bacterial disease caused by Xanthomonas campestris pv. musacearum (Xcm) in enset cultivated areas of the country. The management of Enset Bacterial Wilt (EBW) is important to maximize the crop's yield. Therefore, the present investigation is to determine the disease intensity (prevalence and incidence) of EBW in enset growing areas of Tikur Inchini and Jibat districts of West Shewa, Ethiopia and to evaluate the field grown enset clones for resistance/tolerance to EBW using pot culture condition. Field survey of EBW disease was carried out in the main growing season during September-November, 2012. The disease assessment was made in the enset cultivated fields of selected localities in both districts. The EBW infection was recorded in different levels in both districts. A total of 75 enset cultivated fields were assessed from Tikur Inchini district, of which, 67 fields were affected with different levels of EBW disease prevalence (89.3%). The highest incidence (27%) of EBW was recorded in Waldo Hindhe locality and the lowest incidence was recorded in Homi Hane locality (14 %). From Jibat district, a total of 75 enset cultivated fields were assessed, of which, 65 fields were affected with different levels of disease prevalence (86.7%). The incidence of EBW was recorded highest in Munyo Abayi locality (25%) and the lowest incidence was recorded in Munyo Witate locality (14%). This data indicated that the disease was widely distributed with a very destructive incidence in survey areas of Tikur Inchini and Jibat districts. To evaluate the field grown enset clones for resistance/tolerance to Xcm, twenty number of enset clones collected from both the districts were assessed, using artificial inoculation under pot culture condition. The relative susceptibility of the cultivars to EBW was evaluated three months after inoculation based on wilt incidence. All Xcm inoculated enset clones expanded disease symptoms to different intensity levels after 15 to 30 days inoculation. The varieties of the disease frequency were variable ranging from 19.3 to 100%. Out of the 20 enset clones, only 6 enset clones confirmed a mean infection incidence less than 50 percent. The present investigation displays that the enset genetic copies fluctuate enset bacterial wilt by their reaction. After 30 days of introduction of inoculation, the enset clones 'Warke Bidu', 'Awenyi', and 'Kekar' showed 100 % disease symptoms. The disease symptom was detected from 'Meziya', 'Hiniba', 'Bedadet' and Warke Dima between 21 and 30 days successive inoculation. The remaining enset clones were relatively resistant/tolerant after inoculation of Xcm. Among all, 'Meziya' was found to have the lowest percentage of disease incidence (19.31%) followed by 'Hiniba' (30.18%) and 'Bedadet' (34.26%). Based on the results, none of the enset clones had resistance to Xcm. The results indicated that the enset clones, 'Meziya', 'Hiniba', 'Bedadet' and 'Warke Dima' have exhibited better resistant/tolerant clones to the bacterial wilt, under artificial inoculation conditions and these enset clones should be considered as most tolerant/resistant clones to the pathogen which could be used as a bacterial wilt management component. The results of the study indicated that the use of resistant/tolerant enset clones is one of the best approaches in the management of EBW, cheaper to the farmers and safer to environments. Hence, a resistant and tolerant outcome of the enset clones confirmed by the wilt pathogen should be further assessed in contrast to a great number of Xanthomonas campestris pv. musacearum , isolates in field conditions.

Mouse Cloning Using a Drop of Peripheral Blood1

Somatic cell nuclear transfer (SCNT) is a unique technology that produces cloned animals from single cells. It is desirable from a practical viewpoint that donor cells can be collected noninvasively and used readily for nuclear transfer. The present study was undertaken to determine whether peripheral blood cells freshly collected from living mice could be used for SCNT. We collected a drop of peripheral blood (15-45 μl) from the tail of a donor. A nucleated cell (leukocyte) suspension was prepared by lysing the red blood cells. Following SCNT using randomly selected leukocyte nuclei, cloned offspring were born at a 2.8% birth rate. Fluorescence-activated cell sorting revealed that granulocytes/monocytes and lymphocytes could be roughly distinguished by their sizes, the former being significantly larger. We then cloned putative granulocytes/monocytes and lymphocytes separately and obtained 2.1% and 1.7% birth rates, respectively (P > 0.05). Because the use of lymphocyte nuclei inevitably results in the birth of offspring with DNA rearrangements, we applied granulocyte/monocyte cloning to two genetically modified strains and two recombinant inbred strains. Normal-looking offspring were obtained from all four strains tested. The present study clearly indicated that genetic copies of mice could be produced using a drop of peripheral blood from living donors. This strategy will be applied to the rescue of infertile founder animals or a "last-of-line" animal possessing invaluable genetic resources.

Breaking Down Insulin Resistance

Breaking Down Insulin Resistance

Childhood in Action: A Study of Natality’s Relationship to Societal Change in Never Let Me Go

Introduction Children are our future. This phrase is used so often that it is generally considered to be a cliche, devoid of any insight. If taken seriously, however, it points to the stakes involved in raising and educating society's youngest members. In her theorizing on the political realm, Hannah Arendt posits that children hold the key to renewing the common human world because of their newness, an idea she explains through her concept of natality. Arendt's understanding of political renewal through the actions of new humans places tremendous importance on children. At the same time, the idea that children will inherit stewardship of the political realm can be threatening to adults, which is another of Arendt's insights. These new humans, strangers to the world, require high levels of care and attention because of their dependency and vulnerability, but as they grow up they will make claims on the common human world and will act to change it. Here is a reminder to adults of both their fallibility and their mortality. Given these dynamics, then, it is unsurprising that so many debates and controversies rage over the best ways to raise and educate children. Hanging in the balance is nothing less than the future of the political world itself. To explore these dynamics, I turn to Arendt's writings on the functioning of the political sphere. I ask how children's initial vulnerability and dependency on adults for survival affects their role in society. I highlight Arendt's view, as formulated in The Human Condition and Between Past and Future: Eight Exercises in Political Thought, that natality, the fact that humans are born as radically new creatures, is what gives them the ability to do something new in the common world. However, Arendt also cautions that the child is not yet in a position to put this natality to use in the public sphere; she must be protected from the harsh judgments of that realm and in turn the public realm must be protected from the disruptive newness of the child. (1) I also draw on Deborah Britzman's interpretation of natality in her text The Very Thought of Education: Psychoanalysis and the Impossible Professions. Britzman highlights the relationality of natality: the infant is formed by her first experiences of life through her relationship with her first other (usually her mother) and this sets the stage for her future modes of relating with the world. In order to delve into the implications of natality for society, its unsettling power, and its incredible fragility, I turn to the sketch of human clone children in Kazuo Ishiguro's Never Let Me Go. This novel is a particularly interesting literary object for the study of natality because it depicts a world that will likely seem familiar in some basic ways, with one key difference that is both subtle and striking: the existence of human clones. The uncanny world of the novel thus provides an opportunity for the reader to reflect on the significance of natality because it conjures up characters who live in a similar world to ours but who lack the straightforward relationship to natality that comes from being born to human parents and having experienced the intimate first relationship necessitated by the helplessness of the infant. Technology may change the ways humans arrive in our world in the future, but for now all humans have entered the world as infants from the wombs of human mothers. Thus the novel provides a scenario that can be used as a test case, one whose fictionality can nonetheless illuminate the significance of natality in the world outside the novel. After all, these characters are not some radically new type of creature, completely unrelated to human beings as we understand them. Rather, they are exact genetic copies of humans; they appear to be basically the same kind of beings as the people who live in the cities and towns outside of Hailsham and those who exist in the world the reader inhabits. At its most basic and most literal, natality can simply be considered to name the fact that humans are born--to another human and as a helpless infant. …

Multiploid Inheritance of HIV-1 during Cell-to-Cell Infection

During cell-to-cell transmission of human immunodeficiency virus type 1 (HIV-1), many viral particles can be simultaneously transferred from infected to uninfected CD4 T cells through structures called virological synapses (VS). Here we directly examine how cell-free and cell-to-cell infections differ from infections initiated with cell-free virus in the number of genetic copies that are transmitted from one generation to the next, i.e., the genetic inheritance. Following exposure to HIV-1-expressing cells, we show that target cells with high viral uptake are much more likely to become infected. Using T cells that coexpress distinct fluorescent HIV-1 variants, we show that multiple copies of HIV-1 can be cotransmitted across a single VS. In contrast to cell-free HIV-1 infection, which titrates with Poisson statistics, the titration of cell-associated HIV-1 to low rates of overall infection generates a constant fraction of the newly infected cells that are cofluorescent. Triple infection was also readily detected when cells expressing three fluorescent viruses were used as donor cells. A computational model and a statistical model are presented to estimate the degree to which cofluorescence underestimates coinfection frequency. Lastly, direct detection of HIV-1 proviruses using fluorescence in situ hybridization confirmed that significantly more HIV-1 DNA copies are found in primary T cells infected with cell-associated virus than in those infected with cell-free virus. Together, the data suggest that multiploid inheritance is common during cell-to-cell HIV-1 infection. From this study, we suggest that cell-to-cell infection may explain the high copy numbers of proviruses found in infected cells in vivo and may provide a mechanism through which HIV preserves sequence heterogeneity in viral quasispecies through genetic complementation.

Decreased coronary artery development in Wt1 heterozygous mice

Congenital heart disease is the most common human birth defect which occurs in approximately 1% of all births in Canada. As a major cause of mortality and morbidity, a further understanding of the biological mechanisms underlying congenital heart disease is crucial. Wilms' tumour‐1 (Wt1) was first discovered as a gene mutated in kidney tumour development in children, but has more recently been shown to play an important role in organogenesis. In the developing heart, Wt1 is critical for progenitor cell function. Homozygous Wt1 knockout mice are embryonic lethal with defects in multiple organs, including the heart, kidneys and gonads. Conversely, heterozygous Wt1 (Wt1+/−) mice are reported to be viable and fertile but whether a gene dosage effect exists, specifically related to heart development, remains elusive. In this study, coronary artery formation was investigated in postnatal day one (P1) Wt1+/− mice. Hearts were serially sectioned and immunostained for alpha smooth muscle actin to mark coronary arteries. Amira software was utilized to generate 3‐D reconstructions of the heart to evaluate coronary artery morphology. It was found that coronary artery diameter and coronary artery volume were significantly decreased in Wt1+/−mice compared with Wt1+/+mice at P1. Total body weight, left ventricular, septal and right ventricular myocardial wall thickness were not significantly different between Wt1+/−and Wt1+/+mice at P1. These results demonstrate that expression of both genetic copies of Wt1 is critical for coronary artery development. Ongoing experiments are studying the morphology and function of coronary arteries in the adult Wt1+/− mice. This research is supported by a NSERC Postgraduate Scholarship and the Heart and Stroke Foundation.

S-phase progression in mammalian cells: modelling the influence of nuclear organization

The control of DNA replication is of fundamental importance as cell proliferation demands that identical copies of the genetic material are passed to the two daughter cells that form during mitosis. These genetic copies are generated in the preceding S phase, where the entire DNA complement of the mother cell must be copied exactly once. As part of this process, it is known that different regions of mammalian genomes are replicated at specific times of a temporally defined replication programme. The key feature of this programme is that active genes in euchromatin are replicated before inactive ones in heterochromatin. This separation of S phase into periods where different classes of chromatin are duplicated is important in maintaining changes in gene expression that define individual cell types. Recent attempts to understand the structure of the S-phase timing programme have focused on the use of genome-wide strategies that inevitably use DNA isolated from large cell populations for analysis. However, this approach provides a composite view of events that occur within a population without knowledge of the cell-to-cell variability across the population. In this review, we attempt to combine information generated using genome-wide and single cell strategies in order to develop a coherent molecular understanding of S-phase progression. During this integration, we have explored how available information can be introduced into a modelling environment that best describes S-phase progression in mammalian cells.

Mechanisms regulating S phase progression in mammalian cells

Cell proliferation demands that identical genetic material is passed to daughter cells that form during mitosis. Genetic copies are produced during the preceding interphase, when DNA of the mother cell is copied exactly once. While few processes in biology are regulated with this precision, the fundamental importance cannot be understated as defects might compromise genetic integrity and ultimately lead to cancer. Replication of the human genome in diploid cells occurs during S phase of the cell cycle. Throughout this ~10h period, about 10% of replication units - replicons - are active at any time, even though all potential initiation sites - origins - are established before the onset of S phase. Crucially, the mechanisms that regulate origin selection and define a structured replication programme remain to be defined. We review recent progress in understanding the structure and regulation of S phase and develop a model that we believe best describes the S phase programme in human cells.

Vegetative propagation of patagonian cypress, a vulnerable species from the subantarctic forest of South America

Increasing risks of loosing forest genetic resources and the need for a sustainable quality wood supply make focusing research efforts on undomesticated tree species necessary. The study of their genetic variation in vegetative propagation ability and the development of practical methodologies to obtain genetic copies are essential tools for conservation and breeding programs. patagonian cypress Austrocedrus chilensis is a vulnerable conifer native to the subantarctic forest of South America, with high ecological importance and economical potential. Its genetic diversity, mostly sheltered within unprotected populations, is seriously threatened. This work examined the ability of different genotypes of A. chilensis from xeric, mesic and humid populations to propagate asexually by stem rooting and scion grafting. The influence of exogenous auxins, season of cutting collection, ontogenetic stage of the donor plants, grafting season, and type of scions, was analyzed. Stem rooting ability was found to be poor both for adult (average = 0.27%) and juvenile ortets (average = 2.10%). Only one treatment, a juvenile progeny from a xeric provenance, showed remarkable results with 33.33% of rooting capacity. Grafting showed good results in early spring experiment using vigorous semi-hardwood scions, with an average of 80.95% of successful grafts. Compatibility between genotypes from different provenances used as scion and rootstock was found to be wide. These results indicate that although A. chilensis is a difficult-to-root species, its vegetative propagation by means of scion grafting is feasible using low cost technology.

Dispersal and clonal diversity of North-European parthenogenetic earthworms

At least 15 earthworm species are known to reproduce parthenogenetically. Most of these retain meiosis but the chromosome set is duplicated before meiosis; alternatively there is mitosis instead of meiosis. In both cases the offspring are genetic copies of the parent worm. Parthenogens are always polyploid. Parthenogenesis is associated with a dispersal advantage: a single propagule suffices to establish a new population. We have studied the clone pool structure and dispersal of ecologically dissimilar polyploid parthenogenetic lumbricids in northern Europe using enzyme electrophoresis. The anthropochorous Octolasion cyaneum has a very low number of clones in populations that are located far away from each other. The opposite is the eurytopic Dendrobaena octaedra that has a wide array of clones in each population. The ripicolous Eiseniella tetraedra disperses with flowing water and possibly also through zoochory. On subarctic North-European mountains its clone pool decreases with increasing elevation. At the top there are a few but persistent clones. Small brooks carry propagules downstream, so that at the mouths of brooks clone pools are more diverse than higher up; again larger rivers carry clones downstream. Clone dispersal is relatively free in a freely flowing river, while dams stop propagules in harnessed rivers. The mouths of rivers have high E. tetraedra clone diversity. Clones disperse from these clone centers to islands formed through land uplift along the northern Baltic Sea. The annual turnover of clones is high on these islands. A survey of epigeic and endogeic parthenogens on the Aland islands which serve as stepping stones between Estonia, Finland and Sweden shows an invasion route of clones across the Baltic Sea. Anthropochory (Aporrectodea rosea and Octolasion cyaneum) and hydrochory (E.tetraedra and Dendrobaena octaedra) seem to play important roles in the clone pool formation on the Aland islands. Quite recently an exotic parthenogen Dichogaster bolaui has found a curious habitat in human settlements viz., the sewer pipe system. Many clonal earthworms show significant morphological and morphometric diversity in and between sample localities but we have failed to associate this variation with the clonal variability. It seems that local factors modify the morphometrics and morphology ultimately determined by the genotype of parthenogenetic earthworms.

Genetics and the History of Latin America

Genetics and the History of Latin America

Agro-economic impact of cattle cloning.

The purpose of this paper is to review the economic and social implications of cloned cattle, their products, and their offspring as related to production agriculture. Cloning technology in cattle has several applications outside of traditional production agriculture. These applications can include bio-medical applications, such as the production of pharmaceuticals in the blood or milk of transgenic cattle. Cloning may also be useful in the production of research models. These models may or may not include genetic modifications. Uses in agriculture include many applications of the technology. These include making genetic copies of elite seed stock and prize winning show cattle. Other purposes may range from "insurance" to making copies of cattle that have sentimental value, similar to cloning of pets. Increased selection opportunities available with cloning may provide for improvement in genetic gain. The ultimate goal of cloning has often been envisioned as a system for producing quantity and uniformity of the perfect dairy cow. However, only if heritability were 100%, would clone mates have complete uniformity. Changes in the environment may have significant impact on the productivity and longevity of the resulting clones. Changes in consumer preferences and economic input costs may all change the definition of the perfect cow. The cost of producing such animals via cloning must be economically feasible to meet the intended applications. Present inefficiencies limit cloning opportunities to highly valued animals. Improvements are necessary to move the applications toward commercial application. Cloning has additional obstacles to conquer. Social and regulatory acceptance of cloning is paramount to its utilization in production agriculture. Regulatory acceptance will need to address the animal, its products, and its offspring. In summary, cloning is another tool in the animal biotechnology toolbox, which includes artificial insemination, sexing of semen, embryo sexing and in vitro fertilization. While it will not replace any of the above mentioned, its degree of utilization will depend on both improvement in efficiency as well as social and regulatory acceptance.

Nuclear transfer in cattle.

For decades, a dream of animal breeders has been to clone (make exact genetic copies of) outstanding animals. This was first achieved by splitting embryos (); however, with this technique, only a few animals of the same genetic origin could be produced (). The second approach, which seemed to be more promising, was the embryo reconstruction using a single nucleus from an embryo to an enucleated one-cell embryo. This technique was based on an idea proposed by Spemann in 1938 (). With only few exceptions, experiments on frogs and fish provided scientific evidence that all the cells in the body of an animal appear to contain the same genetic information, being contained in DNA, a molecule located in the nucleus of cells. Thus, within an animal, the DNA sequence in the mammary cells is identical to skin cells. These cells differ in their appearance and function because they utilize different parts of the genetic information, not because the total amount of information differs. Furthermore, all these cells have genetic information present in the one-cell embryo that develop into the animal. Therefore, if the nucleus of any of these cells were used to replace the genetic information in any one-cell embryo, an exact genetic copy of the animal whose cells donated the nucleus would develop. This theory was confirmed by successful experiments in frogs and fish (,). Using similar procedures and inner cell mass cells (ICM) as nuclear donors, Illmensee and Hoppe () reported the birth of live offspring (mice) in 1981. However, these results were never confirmed.