Genetic Ties Research Articles

Joint International Evaluation of Milking Shorthorn Dairy Cattle for Production Traits

Pedigree information and test-day records for the first 3 parities of Milking Shorthorn dairy cattle from 5 countries were analyzed. After editing, the data included 1,018,528 test-day records from 68,653 cows. A multiple-lactation random regression test-day model with Legendre polynomials of order 4 and a Bayesian method were used to estimate variance components for both single and multiple-countries. Fixed effects included herd-test-day class and regressions on DIM within age at calving-parity-season of calving. Random effects included animal genetic, permanent environmental, and residual effects. Average daily heritabilities from single country analyses ranged from 0.33 to 0.47 for milk yield and from 0.37 to 0.45 for protein yield across lactations and countries. Common sires (66) and their daughters were identified for creating a connected data set for simultaneous (co)variance component estimation of milk yield across all 5 countries. Between-country genetic correlations were low, with values from 0.08 to 0.46 and standard deviations from 0.08 to 0.12. Estimated breeding values for milk were generated for each animal using the same test-day animal model. Correlations among country estimated breeding values were higher than genetic correlations. Top 100 bull lists were generated on the scale of each country, and genetic progress was assessed. Future evaluation with increased genetic ties among countries may facilitate international comparison of Milking Shorthorns.

Spare embryos: 3000 reasons to rethink the significance of genetic relatedness

IVF laws in Victoria, Australia provide that human embryos must not remain in storage in excess of 5 years. Studies reviewing the fate of surplus human embryos reveal that close to 90% of couples choose to discard their excess embryos and that hundreds of embryos are disposed of annually. It has been argued that human embryos are a valuable resource and that there is a need to consider educational programmes to encourage couples to donate spare embryos to other infertile couples, rather than discard them. Surveys show that one reason that so few embryos are donated is that couples attach great significance to genetic parenthood. Advances in reproductive technology may necessitate a review of biological definitions of family and the importance of genetic relatedness. It can be argued that it is unreasonable to conclude that genetic ties are so significant that embryos should be discarded rather than donated and raised by non-genetically related parents. It is suggested that education programmes should encourage reflection on people's beliefs about the importance of genetic relatedness with regard to what makes a family. Open embryo donation or directed embryo donation programmes might cause couples to change their minds, or alleviate their anxiety about donating embryos to others.

VARIATION IN ASEXUAL LINEAGE AGE IN POTAMOPYRGUS ANTIPODARUM, A NEW ZEALAND SNAIL

Asexual lineages are thought to be subject to rapid extinction because they cannot generate recombinant offspring. Accordingly, extant asexual lineages are expected to be of recent derivation from sexual individuals. We examined this prediction by using mitochondrial DNA sequence data to estimate asexual lineage age in populations of a freshwater snail (Potamopyrgus antipodarum) native to New Zealand and characterized by varying frequency of sexual and asexual individuals. We found considerable variation in the amount of genetic divergence of asexual lineages from sexual relatives, pointing to a wide range of asexual lineage ages. Most asexual lineages had close genetic ties (∼0.1% sequence divergence) to haplotypes found in sexual representatives, indicating a recent origin from sexual progenitors. There were, however, two asexual clades that were quite genetically distinct (>1.2% sequence divergence) from sexual lineages and may have diverged from sexual progenitors more than 500,000 years ago. These two clades were found in lakes that had a significantly lower frequency of sexual individuals than lakes without the old clades, suggesting that the conditions that favor sex might select against ancient asexuality. Our results also emphasize the need for large sample sizes and spatially representative sampling when hypotheses for the age of asexual lineages are tested to adequately deal with potential biases in age estimates.

Comparação de metodologias de predição de valores genéticos utilizando dados simulados

Foram simuladas, utilizando o programa GENESYS, sete populações com diferentes médias genéticas e estruturas de dados resultantes da substituição de 0, 10, 25, 50, 75, 90 e 100% de reprodutores, com o objetivo de comparar a metodologia de modelos mistos (MMM) com a metodologia GenSys, por meio de suas acurácias e variâncias do erro de predição (PEV), estimadas com base no modelo de reprodutor e no modelo animal. No modelo de reprodutor, à medida que se aumentava a intensidade de seleção, ocorriam diminuição na acurácia e aumento da PEV de ambas as metodologias, em razão da menor acurácia na estimação dos níveis do efeito fixo e da diminuição do número médio de progênies/reprodutor. A superioridade da MMM no modelo de reprodutor foi atribuída à maior acurácia de estimação dos efeitos fixos. No modelo animal, as tendências foram diferentes. Na MMM, à medida que se aumentava a intensidade de seleção, a acurácia se elevava e a PEV permanecia praticamente constante, enquanto, na GenSys, ocorriam diminuição da acurácia e aumento da PEV. O aumento da acurácia, na MMM, decorreu do maior número de conexões genéticas, enquanto a diminuição, na GenSys, foi atribuída à menor acurácia de estimação dos níveis do efeito fixo. A superioridade da MMM foi decorrente da maior acurácia na estimação dos níveis do efeito fixo e do uso da matriz de parentesco completa, que inclui a população-base com indivíduos não-aparentados, não-endogâmicos e não-selecionados. Conclui-se que a MMM foi superior à GenSys, quanto à acurácia e à PEV, para a estrutura de dados selecionados simulada, principalmente para o modelo animal.

Why Parents Play Favorites: Explanations for Unequal Bequests

Economists have invested a great deal of effort in trying to understand the motivation for family transfers, yet recent empirical work testing the seemingly appealing models of altruism and exchange has led to decidedly mixed results. A major stumbling block has been the lack of adequate data. We take a fresh look at the issue using responses to an innovative survey question that directly asks mother about the planned division of their estates. We find that both altruism and exchange are frequently offered as explanations of behavior and are of nearly equal importance. Furthermore, the explanations are consistent with observable characteristics of the mother, lending support to the validity of the question. We also find that among step or adopted families, genetic ties play an important role. Because motivating factors appear to differ across families the lack of a consensus among previous researchers about motives ought not to be surprising.

Recognizing the Threat Posed by an Incestuous Parent to the Victim's Siblings: Part I: Appraising the Risk

Despite unmistakable evidence that incest offenders rarely stop with one child, courts routinely fail to protect an incest victim's siblings. Many courts simple deny that a parent's sex act with one child signals risk to others. Nevertheless, even those courts that acknowledge a sibling's risk reach wildly different results when confronting similar cases. Courts are split over whether a parent who molests his stepchild is equally likely to victimize biological offspring or whether a father who violates a daughter will also victimize sons. There is a substantial body of research about incest that can aid courts to better gauge a sibling's risk. Because the first act of incest creates a corresponding risk to some—but not necessarily all—children in the family, Part I of this 2 part series argues in favor of a presumption of risk that offenders may rebut. Part II examines whether a sibling's gender, genetic ties to the offender, or the offender's treatment mitigate the threat and, consequently, should serve as a basis for rebutting the presumption. Ultimately, this article concludes that the law can safeguard children only if guided by substantial evidence of how abusive families function.

The natural father: genetic paternity testing, marriage, and fatherhood.

The emerging phenomenon of genetic paternity testing shows how good science and useful social reform can run off the rails. Genetic paternity testing enables us to sort out, in a transparent and decisive way, the age-old but traditionally never-quite-answerable question of whether a child is genetically related to the husband of the child's mother. Given the impossibility of settling this question for certain, British and American law has long held that a biological relationship must almost always be assumed to exist. According to what is known as the “marital presumption” or “presumption of legitimacy,” a child born to a woman within a marital relationship is assumed to be the biological child of the woman's husband unless he was absent, impotent, or sterile. In other words, if paternity was not a physical impossibility for the husband, there was a nearly irrebuttable presumption that he was the father of the child. The husband was locked into the role of fatherhood.I am grateful to the participants of Genetic Ties and the Future of the Family, a research project run conjointly by The Hastings Center and the Institute for Bioethics, Health Policy, and Law at the University of Louisville School of Medicine. Discussions held in the course of this project have influenced this paper in various ways. I am especially grateful to Mary Anderlik for detailed comments. An earlier version of this paper was presented at the 2002 annual meeting of the American Society of Bioethics and Humanities and at a colloquium at Oxford University on Genetic Technologies and the Family, and the paper has benefited from comments offered on each of those occasions. Funding for Genetic Ties and the Future of the Family is provided by the National Institutes of Health (grant #HG02485).

The Cradle of Abuse: Evaluating the Danger Posed by a Sexually Predatory Parent to the Victim's Siblings

Despite unmistakable evidence that incestuous parents rarely stop with one child, courts in the US and elsewhere routinely fail to protect an incest victim's siblings. Many courts simple deny that a parent's sex act with one child signals risk to others. But even those courts that acknowledge a sibling's risk reach wildly different results when confronting similar cases. Courts are split over whether a parent who molests his stepchild is equally likely to victimize biological offspring or whether a father who violates a daughter will also victimize sons. Courts reach such fundamentally different conclusions because they operate in a vacuum of sound evidence, without the benefit of expert testimony. This article argues that the substantial body of research about sexually exploited children and incestuous parents can aid courts to better gauge a sibling's risk. Because the first act of incest creates a corresponding risk of some - but not all - children in the family, this article argues in favor of a presumption of risk that offenders may rebut. It then examines whether a sibling's gender or genetic ties to the offender, or the offender's treatment, mitigate the threat and consequently should serve as a basis for rebutting the presumption. The article ultimately concludes the law can safeguard children from this threat of sexual exploitation only if guided by substantial evidence of how abusive families function.

Genetic kinship and social structure in a herd of square‐lipped rhinoceroses (Ceratotherium simum simum) at the zoological center, Tel Aviv/Ramat‐Gan, Israel

AbstractZoos and zoological parks serve as genetic and demographic reserves for strengthening endangered populations and reestablishing extinct populations in the wild. Knowing the genetic ties within captive populations is a very helpful tool for successful reproductive management. In the present study we addressed kinship relationships and behavior among rhinoceroses (Ceratotherium simum simum) raised at the Zoological Center, Tel Aviv/Ramat Gan, Israel, with the hope of identifying reasons for the declining rate of reproduction within the herd. We used the random amplified polymorphic DNA (RAPD) technique to reveal the paternity of the rhinos born at the park. In this way, we identified the paternity of five out of seven young born in the herd, which are currently in Ramat Gan. One male accounted for three (37.5%) births, and two other males accounted for one each. The paternity of the two other animals is unknown and may be of animals that are no longer in the Zoological Center. The genetic determinations were accompanied by behavioral observations, which enabled us to determine the social dynamics in the herd. This study suggests that there are at least three contributing factors to the reproductive decline in the herd: 1) a surplus of males, 2) exclusion of potentially reproductive males from the breeding stock, and 3) specific behavioral and physiological problems in some members of the herd. Zoo Biol 21:561–571, 2002. © 2002 Wiley‐Liss, Inc.

Weighting Factors of Sire Daughter Information in International Genetic Evaluations

International genetic evaluations of dairy bulls are currently based on national genetic evaluation results. Total number of daughters in a country is used to weight national information, but may not optimally reflect the precision of a sire's daughter contribution to international genetic evaluations. This study investigates the impact of alternative weighting factors on international evaluation results. A conventional progeny test scheme was simulated for two dairy cattle populations, with semen exchange at a fixed rate after each generation. True breeding values for both populations were generated as bivariate normal deviates. Each cow had three lactation records in one country only. After 10 generations of selection, all records were used in national breeding value prediction. National breeding values of bulls were used as input to international evaluations. Seven different weighting factors were evaluated: 1) total number of daughters; 2) total number of lactations; 3) as (one) also adjusted for finite contemporary group size; 4) as (three) also adjusted for distribution of daughters over contemporary groups; 5) effective daughter contribution considering finite contemporary group size and correlation between repeated records; 6) as (five) also considering the reliability of the daughter dam evaluation; and 7) as (five) also considering the reliability of the daughter female ancestors’ evaluations. Using the last two weighting factors yielded empirically unbiased estimates of sire variance. Using total number of daughters overestimated genetic variance by up to 7%. In general, international breeding values were marginally affected by choice of weighting factor. The effect was larger when different national evaluation models had been applied in the two countries. International reliabilities for the last two weighting factors were close to expectation, whereas using total number of daughters resulted in 1 to 4% negative bias. In practice, different countries apply a wide range of national evaluation models, and genetic ties may be weak between some populations, thereby increasing the potential effect of weighting factors on international comparisons. The weighting factor developed in this study, which considers contemporary group structure, correlation between repeated records, and reliability of dams of daughters, should replace total number of daughters in international genetic evaluations of dairy sires.

Saccharomyces cerevisiae CTF18 and CTF4 are required for sister chromatid cohesion.

CTF4 and CTF18 are required for high-fidelity chromosome segregation. Both exhibit genetic and physical ties to replication fork constituents. We find that absence of either CTF4 or CTF18 causes sister chromatid cohesion failure and leads to a preanaphase accumulation of cells that depends on the spindle assembly checkpoint. The physical and genetic interactions between CTF4, CTF18, and core components of replication fork complexes observed in this study and others suggest that both gene products act in association with the replication fork to facilitate sister chromatid cohesion. We find that Ctf18p, an RFC1-like protein, directly interacts with Rfc2p, Rfc3p, Rfc4p, and Rfc5p. However, Ctf18p is not a component of biochemically purified proliferating cell nuclear antigen loading RF-C, suggesting the presence of a discrete complex containing Ctf18p, Rfc2p, Rfc3p, Rfc4p, and Rfc5p. Recent identification and characterization of the budding yeast polymerase kappa, encoded by TRF4, strongly supports a hypothesis that the DNA replication machinery is required for proper sister chromatid cohesion. Analogous to the polymerase switching role of the bacterial and human RF-C complexes, we propose that budding yeast RF-C(CTF18) may be involved in a polymerase switch event that facilities sister chromatid cohesion. The requirement for CTF4 and CTF18 in robust cohesion identifies novel roles for replication accessory proteins in this process.

Defining the Subject of Consent in DNA Research

The advent of population-specific genomic research has prompted calls for invention of informed consent protocols that would treat entire social groups as research subjects as well as endow such groups with authority as agents of consent. Critics of such an unconventional ethical norm of “group consent” fear the rhetorical effects of approaching social groups with offers to participate in dialogues about informed consent. Addressing a specific population as the collective subject of genomic research, on this logic, adds currency to the potentially dangerous public opinion that such a group is bound by genetic ties. The paper considers the problem of group and individual identity within the rhetorical dynamics of the discourse and politics of consent.

How Hungry is the Selfish Gene?

We examine resource allocation in step-households in the United States and South Africa to test whether child investments vary according to economic and genetic bonds between parent and child. In the United States, households spend less on food when a child is raised by a nonbiological mother. The reduction is identical for step, adoptive, and foster households, consistent with the hypothesis that genetic ties are the ones that binds. In South Africa, where food spending can be disaggregated, households spend less on milk, fruit and vegetables, and more on tobacco and alcohol, in the absence of a child's birth mother. Family living arrangements have changed dramatically in the United States in a generation. Children in the middle of the century were, on the whole, born to married parents, with whom they lived until adulthood. In the United States today, over half of all children will live apart from at least one parent before reaching age 18 (Bumpass and Sweet, 1989), and a majority of these children will live with a step parent or foster parent. Until recently, most academics were not very concerned about changes in children's family structures. During the 1970s, single parenthood was viewed as a time of transition (Ross and Sawhill, 1975) between divorce and remarriage, and step families were considered to be good substitutes for original twoparent families. Since the 1980s, however, several developments have challenged this optimistic view. First, declines in remarriage have lead to extended periods of high poverty for single mothers and their children, undermining the notion that single parenthood is a time of transition. Second, a growing body of research has shown that children raised by only one of their parents are less successful than children raised by both their parents, when measured across a broad array of outcomes. Although some of these disadvantages are due to characteristics of the parents that predate divorce, there is mounting evidence that parent-absence itself plays at least some causal role in reducing children's life chances. (McLanahan and Sandefur, 1994; Haveman and Wolfe, 1994). A primary mechanism behind the

Genetic Ties in Silk

Genetic Ties in Silk

Non-LTR retrotransposons with unique integration preferences downstream of Dictyostelium discoideum tRNA genes.

Retrotransposable elements are genetic enti ties which move and replicate within host cell genomes We have previously reported on the structures and ge nomic distributions of two non-long terminal repea (non-LTR) retrotransposons, DRE and Tdd-3, in the eukaryotic microorganism Dictyostelium discoideum DRE elements are found inserted upstream, and Tdd-3 elements downstream, of transfer RNA (tRNA) genes with remarkable position and orientation specificities The data set currently available from the Dictyostelium Genome Project led to the characterisation of two repetitive DNA elements which are related to the D. discoideum non-LTR retrotransposon Tdd-3 in both their structural properties and genomic distributions. It appears from our data that in the D. discoideum genome tRNA genes are major targets for the insertion of mobilised non-LTR retrotransposons. This may be interpreted as the consequence of a process of coevolution, allowing a viable population of retroelements to transpose without being deleterious to the small microbial host genome which carries only short intergenic DNA sequences. A new nomenclature is introduced to designate all tRNA gene-targeted non-LTR retrotransposons (TREs) in the D. discoideum genome. TREs inserted 5' and 3' of tRNA genes are named TRE5 and TRE3, respectively. According to this nomenclature DRE and Tdd-3 are renamed TRE5-A and TRE3-A, respectively. The new retroelements described in this study are named TRE3-B (formerly RED) and TRE3-C.

Social versus Biological Parenting: Family Functioning and the Socioemotional Development of Children Conceived by Egg or Sperm Donation

By investigating egg donation families, donor insemination families, adoptive families, and families created by in vitro fertilization, the aim of the present study was to examine parents' emotional well-being, the quality of parenting, and childrens' socioemotional development in families with a child who is genetically unrelated to the mother or the father. The differences that were found to exist between families according to the presence or absence of genetic ties between parents and their children reflected greater psychological well-being among mothers and fathers in families where there was no genetic link between the mother and the child. The families did not differ with respect to the quality of parenting or the psychological adjustment of the child.

Relationships between energy balance and health traits of dairy cattle in early lactation

AbstractData were records of daily food intake and milk production, periodic measures of milk composition and all health and reproductive information from 140 multiparous Holstein cows involved in various experiments at the Agriculture Canada dairy research station in Lennoxville, Quebec. Energy concentrations of the total mixed rations were also available. Daily energy balance was calculated by multiplying the food intake by the concentration of energy in the diet and then subtracting from this quantity the expected (National Research Council) amount of energy required for maintenance (based on parity and body weight) and for milk production (based on yield and concentrations of fat, protein and lactose). Four energy balance traits were defined: (1) average daily energy balance within the first 10 to 100 days of lactation, (2) minimum daily energy balance, (3) days in negative energy balance and (4) total energy deficit during the period of negative energy balance. Health traits were the numbers of incidences of each of the following: (1) all udder problems, (2) mastitis, (3) all locomotive problems, (4) laminitis, (5) digestive problems and (6) reproductive problems. Reproductive traits were the number of days to first observed oestrous and number of inseminations. Phenotypic relationships between energy balance and health were investigated by regressing the energy balance traits on each health trait. Parity and treatment (according to the research trial that the cow was involved with) were also included in the model. Genetic parameters were estimated with restricted maximum likelihood and a model that included effects of parity, treatment and animal. Phenotypically, several significant (P<0.10) relationships between energy balance and health were observed. Cows with longer periods of negative energy balance had increased digestive problems. Cows with greater total energy deficit had more digestive problems and laminitis. Estimates of heritabilities for energy intake and milk energy were 0.42 and 0.12, respectively but estimates of heritability for all energy balance traits were zero. The low estimates for these traits may have been due to (1) low true additive genetic variance, (2) small amount of data, or (3) relatively few genetic ties among cows.

Genetic counseling: clinical and ethical challenges.

After explaining the origin, nature, and goals of genetic counseling, we consider the impact of the Human Genome Project on its practice. In light of the availability of presymptomatic tests for late-onset disorders and the possibility of preventive behavior or treatment, we examine the apparent conflict between nondirectiveness and directiveness in genetic counseling. We discuss views of genetic counselors, medical geneticists, and counselees on specific issues, and document gender differences in attitudes toward genetic ties to offspring. Because genetic discrimination and unequal access to genetic services are likely to increase with advances in genetics, we conclude that efforts of genetic counselors to adhere to the principle of justice or equity in their practice cannot be successful without governmental and public support, as well as support from researchers and colleagues in health care.

The description of a unique population with a very high prevelance of localized juvenile periodontitis

The reported prevalence of localized juvenile periodontitis (LJP) amongst teenagers and young adults varies greatly. The etiology of LJP has been related to Actinobacillus actinomycetemcomitans (Aa), and it has also been suggested that there may be a transmission of Aa within families resulting in the familial distribution of the disease. This study describes the high prevalence of LJP in adolescents, 12-20 years of age, from a group of nuclear families living and functioning in a closed, closely knit community. The survey was carried out on a population of teenagers that had attended the same school and their siblings. All students attending that school and their siblings were examined. They were given a periodontal examination and a questionnaire relating to their demographic details and their personal oral hygiene habits. The periodontal examination was limited to the incisors and first molar teeth. Plaque index (PlI), gingival index (GI), the presence or absence of bleeding on probing (BOP), probing pocket depth (PPD) and recession were measured. All patients having at least two of the examined sites with probing pocket depth > or =5 mm or one site > or =6 mm were considered as possible sufferers from LJP and had a full mouth periapical radiographic survey carried out using a paralleling technique to confirm the diagnosis. At the sites with probing pocket depth > or =5 mm, a Shei ruler was used to measure the % of the root coronal to the alveolar bone. A cut off point of > or =20% was used as a measure of true bone loss confirming the clinical diagnosis of LJP. 86 individuals from 30 families comprised the population of interest. There were 44 males and 42 females with a mean age of 14.7+/-2.3. Of the 86 individuals examined, 33 individuals from 15 families were diagnosed as having LJP (38.4%). None of the individuals examined showed any evidence of the generalized form of juvenile periodontitis. The mean age of the LJP patients was 15+/-2.3 yrs. with a 1:1.75 male to female ratio. Except for 2 pairs of families with genetic ties, no familial connections could be traced between the different nuclear families affected by LJP despite repeated and intensive questioning. There were no significant differences in the PlI and the GI between the groups while the LJP group had significantly higher BOP, PPD and PAL than the non-LJP group. These finding strongly suggest an environmental influence in the etiology of the disease.

Genetic links, family ties, and social bonds: rights and responsibilities in the face of genetic knowledge.

Currently, some of the most significant moral issues involving genetic links relate to genetic knowledge. In this paper, instead of looking at the frequently addressed issues of responsibilities professionals or institutions have to individuals, I take up the question of what responsibilities individuals have to one another with respect to genetic knowledge. I address the questions of whether individuals have a moral right to pursue their own goals without contributing to society's knowledge of population genetics, without adding to their family's knowledge of its genetic history, and without discovering genetic information about themselves and their offspring. These questions lead to an examination of the presumed right to genetic ignorance and an exploration of a variety of social bonds. Analyzing cases in light of these considerations leads to a surprising conclusion about a widely accepted precept of genetic counseling, to some ethical insights into typical problems, and to some further unanswered questions about personal responsibility in the face of genetic knowledge.