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PubMed2006

Genetics of growth and reproduction in the turkey. 16. Effect of repeated backcrossing of an egg line to a commercial sire line.

The turkey industry's view of the relative economic importance of growth and egg production has changed rapidly, and genetic changes by selection within lines may not be rapid enough to meet the changing needs. The objective of the present study was to determine the feasibility of rapidly increasing the BW of dam lines by repeated backcrossing of a dam line (E) to a commercial sire line (B). The experimental E line was selected long-term for increased egg production and was used as the model for a turkey dam line. The B line was larger (more than 3-fold) in BW at 8, 16, and 20 wk of age, had wider breasts (approximately 1.8-fold) at 16 wk of age, and had lower egg production for 180 d (about 3-fold) than the E line. Based on additive genetic variation, males in the F1 generation of the B x E cross did not differ from expected in BW at any age, but females of this cross had BW less than expected at 16 and 20 wk of age. In the F1 generation, breast width of the cross did not differ from the expected value, but egg production for 180 d was greater than expected (126.6 vs.102.3 eggs/hen). After 3 generations of backcrossing, the backcrosses exhibited a gain in 20-wk BW of 12.5 and 8.8 kg, respectively, for males and females; a gain of 5.9 and 5.3 cm in breast width at 16 wk of age for males and females, respectively; and a loss of 74.1 eggs per hen over a 180-d production period. Based on the results of the current and a previous study, limited backcrossing of a dam line to a sire line may be an economically feasible method to greatly increase the BW of dam lines without unduly sacrificing egg production. For maximum gains per generation, backcrossing probably should be used for a maximum of 2 or 3 generations.

Animals↗
PubMed2002

Preservation of the wild European mouflon: the first example of genetic management using a complete program of reproductive biotechnologies.

Although the potential use of reproductive biotechnologies for safeguarding endangered wildlife species is undoubted, practical efforts have met with limited success to date. In those instances in which modern technologies have been adapted to rescuing rare or endangered species, procedures have been applied piecemeal, and no consistent breeding program based on reproductive biotechnologies has been undertaken. Here we describe for the first time the rescue of an endangered species, the European mouflon (Ovis orientalis musimon), by the application of an integrated package of reproductive biotechnologies. This genetic management extended from the initial collection of gametes, through the in vitro production of embryos and interspecific transfer, to the birth of healthy mouflon offspring. In addition, a genetic resource bank for the European mouflon was established, with cryopreserved sperm, embryos, and somatic cells.

Animals↗
PubMed2003

Developmental genetics of the female reproductive tract in mammals.

The female reproductive tract receives the oocytes for fertilization, supports the development of the fetus and provides the passage for birth. Although abnormalities of this organ system can result in infertility and even death, until recently relatively little was known about the genetic processes that underlie its development. By drawing primarily on mouse mutagenesis studies and the analysis of human mutations we review the emerging genetic pathways that regulate female reproductive-tract formation in mammals and that are implicated in congenital abnormalities of this organ system. We also show that these pathways might be conserved between invertebrates and mammals.

Animals↗
PubMed2004

Genetic relationships between persistency and reproductive performance in first-lactation Canadian holsteins.

The main objective of this study was to estimate genetic relationships between lactation persistency and reproductive performance in first lactation. Relationships with day in milk at peak milk yield and estimated 305-d milk yield were also investigated. The data set contained 33,312 first-lactation Canadian Holsteins with first-parity reproductive, persistency, and productive information. Reproductive performance traits included age at first insemination, nonreturn rate at 56 d after first insemination as a virgin heifer and as a first-lactation cow, calving difficulty at first calving and calving interval between first and second calving. Lactation persistency was defined as the Wilmink b parameter for milk yield and was calculated by fitting lactation curves to test day records using a multiple-trait prediction procedure. An 8-trait genetic analysis was performed using the Variance Component Estimation package (VCE 5) via Gibbs sampling to estimate genetic parameters for all traits. Heritabilities of persistency, day in milk at peak milk yield and estimated 305-d milk yield were 0.18, 0.09 and 0.45, respectively. Heritabilities of reproduction were low and ranged from 0.03 to 0.19. The highest heritability was for age at first insemination. Heifer reproductive traits were lowly genetically correlated, whereas cow reproductive traits were moderately correlated. Heifers younger than average when first inseminated and/or conceived successfully at first insemination tended to have a more persistent first lactation. First lactation was more persistent if heifers had difficulty calving (r(g) = 0.43), or conceived successfully at first insemination in first lactation (r(g) = 0.32) or had a longer interval between first and second calving (r(g) = 0.17). Estimates of genetic correlations of reproductive performance with estimated 305-d milk yield were different in magnitude, but similar in sign to those with persistency (0.02 to 0.51).

Animals↗
PubMed2000

The genetic revolution in artificial reproduction: a view of the future.

With the completion of the human genome project, micro-array technology offers the potential to open up a whole new vista in assisted reproduction. In the next 10-20 years we will be able to screen each human embryo for all numerical chromosomal abnormalities as well as many genetic diseases. Micro-array analysis may permit the screening of multiple alleles for monogenetic diseases and polygenic diseases, including diabetes, hypertension and schizophrenia. In the near future, it may be possible to assess an individual's genetic predisposition for cardiovascular disease, all types of cancer and infectious diseases. In the distant future, it may even be possible to screen for any genetic trait, e.g. stature, baldness, obesity, hair colour, skin colour or even IQ. Although it is still uncertain what molecular genetic tools may be available, we can be sure that some of these trends will have major consequences on the future of assisted reproduction and society at large.

Chromosome Aberrations↗
PubMed2006

Porcine reproductive and respiratory syndrome virus strains of exceptional diversity in eastern Europe support the definition of new genetic subtypes.

Porcine reproductive and respiratory syndrome virus (PRRSV) ORF5 and ORF7 sequences from Belarus were found to be of the European (EU) genotype, but grouped separately from all other EU genotype sequences described so far, including live-attenuated EU genotype PRRSV vaccines and Italian EU genotype sequences, some of which have been associated with reduced vaccine efficacy. Also, the Belarusian EU-PRRSV exhibited extreme ORF7 size polymorphism, ranging from 375 nt (the smallest EU genotype ORF7 yet described) to 393 nt (the largest ORF7 yet described for any arterivirus). With the Belarusian sequences, the diversity of EU genotype PRRSV now exceeds that of the North American (US) genotype PRRSV, suggesting a European origin of PRRSV. Finally, a very sharp geographical demarcation of highly diverse EU genotype PRRSV was observed along the eastern Polish border. The new Belarusian sequences have relevance for vaccine and diagnostic-antigen design and show that sequence analysis of PRRSV from more eastern parts of Europe may offer further insights into the emergence and evolution of PRRSV.

Animals↗
PubMed2002

Consequences of hierarchical allocation for the evolution of life-history traits.

Resource allocation within individuals may often be hierarchical, and this may have important effects on genetic correlations and on trait evolution. For example, organisms may divide energy between reproduction and somatic growth and then subdivide reproductive resources. Genetic variation in allocation to pathways early in such hierarchies (e.g., reproduction) can cause positive genetic correlations between traits that trade off (e.g., offspring size and number) because some individuals invest more resources in reproduction than others. We used quantitative-genetic models to explore the evolutionary implications of allocation hierarchies. Our results showed that when variation in allocation early in the hierarchy exceeds subsequent variation in allocation, genetic covariances and initial responses to selection do not reflect trade-offs occurring at later levels in the hierarchy. This general pattern was evident for many starting allocations and optima and for whether traits contributed multiplicatively or additively to fitness. Finally, artificial selection on a single trait revealed masked trade-offs when variation in early allocation was comparable to subsequent variation in allocation. This result confirms artificial selection as a powerful, but not foolproof, method of detecting trade-offs. Thus, allocation hierarchies can profoundly affect life-history evolution by causing traits to evolve in the opposite direction to that predicted by trade-offs.

Animal Population Groups↗
PubMed1984

Human genetic technology: who shall control?

The biotechnical "revolution" has fast come upon us. It promises to produce both substantial benefits and difficult dilemmas for individuals and society. Despite the growing attention being paid to biotechnology, a major unanswered question is who shall control the development and use of the powerful array of human genetic and reproductive innovations. Should the decisions be left to individual consumers and private industry or should they be made by the government or other social institutions? After briefly reviewing development in human genetics and reproduction and describing trends toward commercialization of them, this article discusses the dilemmas these trends raise for a democratic society. It argues for the urgent need to delineate societal goals and priorities for the future and for technology assessment as early as possible in the developmental process. The article concludes by presenting some examples of the social policy problems now emerging.

Biotechnology↗
PubMedDate not supplied

Genetic variation and genetic load due to the male reproductive component of fitness in Drosophila.

The genetic variation and genetic load due to virility, the male reproductive component of fitness, was measured in Drosophila melanogaster and D. pseudoobscura using males homozygous and heterozygous for the second chromosome of each species. Virility was determined in a female-choice, male mating competition experiment where both mating propensity and fertility were taken into account.--The mean virility of the homozygous D. melanogaster males relative to the heterozygous males was 0.50; the relative mean virility of the quasinormal homozygotes was 0.56. The mean virility of the homozygous D. pseudoobscura males relative to the heterozygous males was 0.70; the relative mean virility of the nonsterile homozygotes was 0.72, and of the quasinormal homozygotes, 0.68.--Depending on the species and chromosome sampled, fertile homozygous males had a mean virility 15 to 50% lower than the mean viability of individuals homozygous for a chromosome with quasinormal viability. The genetic load due to virility was also greater than that due to the female reproductive component. This higher level of hidden genetic variation (or genetic load) indicates that the results of Prout (1971a, b) and Bundgaard and Christian (1972), where the virility component of fitness dominated the dynamics of an artificial polymorphism, may be more general and that virility may dominate the dynamics of natural polymorphisms as well.

Animals↗
PubMed1994

Genetic analysis of male reproductive contributions in Chamaelirium luteum (L.) gray (Liliaceae).

Genealogical analysis is a powerful tool for analysis of reproductive performance in both natural and captive populations, but assignment of paternity has always been a stumbling block for this sort of work. Statistical methods for determining paternity have undergone several phases of development, ranging from straightforward genetic exclusion to assignment of paternity based on genetic likelihood criteria. In the present study, we present a genetic likelihood-based iterative procedure for fractional allocation of paternity within a progeny pool and apply this method to a population of Chamaelirium luteum, a dioecious member of the Liliaceae. Results from this analysis clearly demonstrate that different males make unequal contributions to the overall progeny pool, with many males contributing essentially nothing to the next generation. Furthermore, the distribution of paternal success among males shows a highly significant departure from (Poisson) randomness. The results from the present analysis were compared with earlier results obtained from the same data set, using likelihood-based categorical paternity assignments. The general biological pattern revealed by the two analyses is the same, but the estimates of reproductive success are only modestly (though significantly) correlated. The iterative procedure makes more complete use of the data and generates a more sharply resolved distribution of male reproductive success.

Genotype↗
PubMed2004

Regulating preimplantation genetic diagnosis--how to control PGD.

PURPOSE: To assess the regulations for Preimplantation Genetic Diagnosis (PGD). How to regulate and control PGD. Is any special licensing procedure necessary? METHODS: A review of the statements of the organization and the Japan Society of Obstetrics and Gynecology (JSOG). Also, we assess the JSOG guidelines for PGD and the statements on diagnosis of genetic diseases of the Japan Society of Human Genetics. We discuss extra licenses and qualifications for laboratories, staff, and directors. RESULTS: At present, there are no regulations governing PGD for laboratories, scientists, directors, and staff. Regulations are set by committees and organizations of the countries involved. We don't have any worldwide system of controls. In Japan, we are considering regulations in the fields of reproduction and genetics. CONCLUSIONS: PGD requires high-level techniques in taking samples, and high-level knowledge about genetic diseases. In diagnosis, we have to be as close to 100% accurate as possible. However, samples for PGD are so small that there is always a risk of failure. Also, we are required to have highly specialized knowledge about reproduction and genetics. In Japan, JSOG has a plan to join with the Society for Investigating Infertility and Society for Genetics.

Female↗
PubMed1996

Genetic variation in porcine reproductive and respiratory syndrome virus isolates in the midwestern United States.

The nucleotide sequence of a 3266 bp region encompassing open reading frames (ORFs) 2 through 7 of the porcine reproductive and respiratory syndrome virus (PRRSV) was determined for 10 isolates recovered from the midwestern United States. Pairwise comparisons showed that genetic distances between isolates ranged from 2.5% to 7.9% (mean 5.8% +/- 0.2%) whereas the Lelystad strain from Europe was, on average, 34.8% divergent from US clones. Thus, US and European PRRSV isolates represent genetically distinct clusters of the same virus. ORF 5, which encodes the envelope glycoprotein, was the most polymorphic [total nucleotide diversity (pi) = 0.097 +/- 0.007] and ORF 6, encoding the viral M protein, was the most conserved (pi = 0.038 +/- 0.003). The substantial differences in nucleotide diversity among ORFs suggests that the virus is evolving by processes other than simple accumulation of random neutral mutations. In support of this hypothesis, statistical analyses of the nucleotide sequence provided strong evidence for intragenic recombination or gene conversion in ORFs 2, 3, 4, 5 and 7, but not in ORF 6. An excess of synonymous (silent) substitutions was observed in all six ORFs, indicating an evolutionary pressure to conserve amino acid sequences. Taken together, the data indicate that despite intragenic recombination among extant PRRSV isolates, purifying selection has acted to maintain the primary structure of individual ORFs.

Animals↗