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PubMed1995

Genetic mapping of quantitative trait loci for traits with ordinal distributions.

Statistical methods for mapping quantitative trait loci relative to genetic markers are now well established for continuous traits with normal distributions. However, many traits of economic importance are recorded on a discrete, ordinal scale. Here we describe a model developed for the analysis of ordinal traits, such as degree of difficulty in calving or categories of plant disease resistance. The model estimates the distance from the quantitative trait locus to neighbouring genetic markers, and also genetic parameters, either as gene effects on an underlying continuous scale or as probabilities of the observed categories. The model is tested on simulated data and is compared with an analysis based on mixtures of normal distributions. The ordinal model is found to estimate the parameters more accurately, especially when the number of categories is small or when only one linked marker is available.

Animal Husbandry↗
PubMed1996

Second malignant neoplasms among long-term survivors of ovarian cancer.

Second malignant neoplasms were evaluated among 32,251 women with ovarian cancer, including 4,402 10-year survivors, within the nine population-based registries of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute (1973-1992) and the Connecticut Tumor Registry (1935-1972). Overall, 1,296 second cancers occurred against 1,014 expected [observed/expected (O/E), 1.28; 95% confidence interval (CI), 1.21-1.35]. Sites contributing 25 or more excess cancers included leukemia (O/E, 4.17; O, 111; 95% CI, 3.43-5.03) and malignancies of colon (O/E, 1.33; O, 188; 95% CI, 1.15-1.54), rectum (O/E, 1.43; O, 76; 95% CI, 1.13-1.79), breast (O/E, 1.18; O, 404; 95%, CI 1.07-1.30), and bladder (O/E, 2.07; O, 65; 95% CI, 1.59-2.63). Ocular melanoma (O/E, 4.45; O, 8; 95% CI, 1.92-8.77) was also significantly increased. Second cancer risk was high during all follow-up intervals, and cumulative risk at 20 years was 18.2%, compared with a population expected risk of 11.5%. Statistically significant relationships existed between serous adenocarcinoma of the ovary and breast cancer (O/E, 1.29; 95% CI, 1.06-1.56) and mucinous ovarian adenocarcinoma and rectal cancer (OE/E, 1.95; 95% CI, 1.09-3.22). Secondary leukemia appeared linked with antecedent chemotherapy, whereas radiotherapy was associated with cancers of connective tissue, bladder, and possibly pancreas. Genetic and reproductive factors predisposing to ovarian cancer may have contributed to the elevated risk of breast and colorectal neoplasms and possibly ocular melanoma. Thus, excess malignancies following ovarian cancer represent complications of curative therapies and/or underlying susceptibility states that have etiological and clinical ramifications.

Adult↗
PubMed1997

Pheromones of the ciliate Euplotes octocarinatus not only induce conjugation but also function as chemoattractants.

Cells of the ten mating types of the ciliate Euplotes octocarinatus communicate by pheromones before they enter conjugation. The pheromones induce homotypic pairing when applied to mating types that do not secrete the same pheromone(s). Heterotypic pairs (i.e., those between cells of different mating types) are formed only when both mating types in a mixture secrete a pheromone that the other does not. The genetics of mating types is based on four codominant mating type alleles, each allele determining production of a different pheromone. Here we report that the pheromones not only induce pair formation but also attract cells. This was shown by placing cells of various mating types in neighboring agar wells so that the pheromones could diffuse from one well to the next. We found that the cells accumulated on the side of the well where a pheromone entered by diffusion. This response was observed only if the pheromone had the capacity to induce the cells to conjugate. That the pheromones and not some other substances attract the cells was shown by placing pheromone 3, expressed in Escherichia coli, in wells next to tester strains. Mating types known to respond to pheromone 3 by pair formation also showed accumulation on the side of the well at which the pheromone entered by diffusion. Since the pattern of cell attraction corresponds with the pattern of conjugation induction, we suggest that not only conjugation induction but also cell attraction is governed by pheromone-specific receptors. In addition, we describe a succession of changes in the behavior of cells affected by the pheromones.

Animals↗
PubMed2003

Inheritance of reproductive traits of female common ducks (Anas platyrhynchos) in pure breeding and in inter-generic crossbreeding with muscovy ducks (Cairina moschata).

1. Genetic parameters of reproductive traits were estimated in a population of common duck, in purebreeding and crossbreeding (with Muscovies) insemination systems. A total of 989 females were studied over three generations as well as 4025 purebred offspring and 4,125 male mule offspring. 2. Traits studied were age at first egg, total number of eggs laid until the age of 48 weeks, fertility and hatchability rates in pure and crossbreds, weight at 6 and 30 weeks of age, average egg weight and body weight of the male mule ducks at 6 weeks of age. 3. Heritability estimates were found to be medium range for reproductive traits (0.15 to 0.47). Heritability value for fertility or hatchability in crossbreds was twice as high as in purebreds (0.32 vs 0.15 for fertility; 0.36 vs 0.16 for hatchability). 4. Fertility in purebreeding and in crossbreeding were two different traits (r(g) = 0.49) while hatchability displayed a high genetic correlation between breeding systems (r(g) = 0.88). 5. Genetic correlations with number of hatched mule ducks were medium or high and favourable. Genetic correlations between reproductive traits and weights were low (< 0.36), the most related trait being the body weight of the male mule duck at 6 weeks of age.

Animals↗
PubMed2005

Genetic basis of drought resistance at reproductive stage in rice: separation of drought tolerance from drought avoidance.

Drought tolerance (DT) and drought avoidance (DA) are two major mechanisms in drought resistance of higher plants. In this study, the genetic bases of DT and DA at reproductive stage in rice were analyzed using a recombinant inbred line population from a cross between an indica lowland and a tropical japonica upland cultivar. The plants were grown individually in PVC pipes and two cycles of drought stress were applied to individual plants with unstressed plants as the control. A total of 21 traits measuring fitness, yield, and the root system were investigated. Little correlation of relative yield traits with potential yield, plant size, and root traits was detected, suggesting that DT and DA were well separated in the experiment. A genetic linkage map consisting of 245 SSR markers was constructed for mapping QTL for these traits. A total of 27 QTL were resolved for 7 traits of relative performance of fitness and yield, 36 QTL for 5 root traits under control, and 38 for 7 root traits under drought stress conditions, suggesting the complexity of the genetic bases of both DT and DA. Only a small portion of QTL for fitness- and yield-related traits overlapped with QTL for root traits, indicating that DT and DA had distinct genetic bases.

Analysis of Variance↗
PubMed1999

Effect of genetic merit and concentrate feeding on reproduction of grazing dairy cows in a subtropical environment.

This study was conducted to determine the effects of genetic merit for milk production and concentrate feeding on the intervals to the onset of postpartum cyclic ovarian activity, first insemination, and establishment of pregnancy. Other factors considered included biochemical measures of energy balance, liveweight, and measures of production. A farmlet study was conducted with two lines of cattle that differed in Australian Breeding Value by 735 L milk and 47 kg of fat plus protein that were fed 300 or 2000 kg of concentrate per cow per year in a subtropical grazing system based on ryegrass, clover, and kikuyu pasture. Milk yield was higher in cows fed 2000 kg of concentrate per cow per year (23.6 L/d) than those fed 300 kg/cow per year (18.2 L/d), and cows of medium genetic merit (19.6 L/d) produced less milk than those of high genetic merit (22.2 L/d). Plasma glucose concentration was lower in the cows of high genetic merit (3.11 mmol/L), than in the cows of medium genetic merit (3.39 mmol/L). The cumulative probabilities of ovulation, insemination, and establishment of pregnancy by any day postpartum were determined by a Weibull distribution. Medium genetic merit cows in winter were more likely to ovulate by any day postpartum than in summer and more likely than high genetic merit cows in either summer or winter. The cumulative probability of insemination was lower in primipara than multipara and in summer than in winter. Primiparous cattle had a lower cumulative probability of pregnancy by any day postpartum.

Animal Feed↗
PubMed2005

In one's own image: ethics and the reproduction of deafness.

The ethics of the use of genetic screening and reproductive technologies to select against and for deafness is presented. It is argued that insofar as deafness is a disability it is ethical to act in such a way as to avoid the conception or birth of children with genetic or congenital deafness. The discovery and recognition of signing deaf communities as cultural and linguistic communities (minorities) does not alter this basic ethical position, although the consequences of widespread application of this technology appears destined to lead to the eventual disappearance of these communities. The argument that acting to avoid deafness is unethical because it will lead to the elimination of a linguistic or cultural group (genocide or ethnocide) or conversely that acting to ensure deafness is ethical, if not praiseworthy, can only be sustained if deafness is not regarded as a disability at all. I argue that the premise that deafness is not a disability of some sort is false and thus the claim that genetic selection against deafness is unethical is untenable.

Adult↗
PubMed1994

Genetics of a pheromonal difference contributing to reproductive isolation in Drosophila.

Although sexual isolation is one of the most important causes of speciation, its genetic basis is largely unknown. Here evidence is presented that suggests that sexual isolation between two closely related species of Drosophila is largely caused by differences in female cuticular hydrocarbons. This difference maps to only one of the three major chromosomes, implying that reproductive isolation might have a fairly simple genetic basis. The effect of the hydrocarbons on courtship may help explain the ubiquitous asymmetry of sexual isolation between many pairs of Drosophila species.

Animals↗
PubMed1985

Estimates of genetic correlations between testicular measurements and female reproductive traits in cattle.

Data from 528 male and 645 female progeny of 63 sires were used to estimate genetic correlations between female and male reproductive traits. Data were from two Hereford herds involved in a long-term selection program of the North Carolina Agricultural Experiment Service. Testicular measurements of circumference, diameter, length and volume were obtained on bulls at 205 and 365 d. Testicular growth measures were defined as differences between 205-and 365-d measurements. Heifers were placed in the breeding herd as yearlings and given two breeding seasons to produce a calf. Traits utilized from females were three age-at-first-breeding traits, two age-at-first-calving traits, two pregnancy rate traits, rebreeding interval and calving interval. Genetic correlations were estimated from half-sib and from sire-daughter analyses. Seventy-five percent or more of the correlations of testicular measurements with pregnancy rats, age at first breeding and age at first calving were in the favorable direction. Average correlations were .62, -.55 and -.66, respectively. For each of the remaining female traits, approximately 50% of the correlations were favorable and the average correlations were small. Correlations were summarized by testicular measurement with favorable correlations given a negative sign. Testicular diameter had more favorable correlations (80%) than length, volume or circumference (70%). However, average correlations were similar (-.31, -.30, -.34 and -.26, respectively). Testicular measurements taken at either 205 or 365 d had the same percentage of favorable correlations (72%), while testicular growth measurements had a slightly higher percentage of favorable correlations (78%). Average correlations of 365-d measures were higher (-.38) than either 205-d or growth measures (-.25 and -.28, respectively). Heritabilities for testicular measurements tended to be moderate to high, while those for female reproduction tended to be low to moderate. These results suggest that selection for increased testicular size would lead to improvement in female reproduction, particularly an increase in calving rate and a decrease in age at first breeding.

Animals↗
PubMed1989

Psychological aspects of genetic counseling: VI. A critical review of the literature dealing with education and reproduction.

The post-1979 literature dealing with the educational and reproductive outcome and process of genetic counseling is reviewed. Despite methodological difficulties, recent publications strongly suggest that genetic counseling is successful in educating counselees about diagnostic and risk information. In general, investigators suggest that there is room for improvement and the factors leading to imperfect recall of information need to be elucidated. Process studies suggest that the educational priorities of counselors and counselees may not always be consistent. The contribution of these inconsistencies to outcome measures needs further study. Also, it appears that differing counseling approaches may be equally effective in achieving educational goals. Studies on the reproductive outcome of genetic counseling show no strong impact of counseling; there appears to be a net increase of desire for more children following counseling. Precounseling reproductive intentions, rather than counseling, were found to be a major factor in determining postcounseling outcome. Process studies suggest that although many counselees say that they were influenced by genetic counseling, it is uncertain what they mean, since for many counselees, reproductive decisions seem to have been made prior to counseling.

Attitude to Health↗
PubMed2001

A genome-wide survey of reproductive barriers in an intraspecific hybrid.

Genetic study of the reproductive barriers between related species plays an essential role in understanding the process of speciation. We developed a new method for mapping all possible factors causing deviations from expected Mendelian segregation ratios in F(2) progeny, which substantially contribute to reproductive isolation. A multiresponse nonlinear regression analysis of the allele frequencies of the markers covering an entire genome in the F(2) population was performed to estimate the map position and intensity of the reproductive barriers on each chromosome. In F(2) plants from a cross between a Japonica variety of rice, Nipponbare, and an Indica variety, Kasalath, the deviations of allele frequencies were well explained by 33 reproductive barriers. Of these, 15 reproductive barriers affected the allele transmission rate through the gametophyte and in 9 of these 15 cases, an Indica allele was transmitted at a higher frequency than a Japonica allele. The other 18 reproductive barriers altered the viability of the zygote via its genotype. Two zygotic reproductive barriers showed overdominance and 5 showed underdominance. The most pronounced reproductive barrier, mapped at 62.3 +/- 0.4 cM on chromosome 3, transmitted the Indica allele by 94% through the male gametophyte. The accuracy of the barrier position in the regression analysis was confirmed by progeny analysis. The regression analysis proved to be a powerful tool for detecting and characterizing every reproductive barrier, irrespective of whether it acted on the male or female gametophyte or the zygote.

Chromosome Mapping↗
PubMed1980

Genetic polymorphisms of blood and milk and reproduction in Holstein cattle.

Associations of blood and milk protein polymorphisms with reproductive performance were examined in more than 32,000 services in 15,000 service periods of 6,000 cows and 700 service sires in Holsteins. Seven blood groups, one serum protein, and four milk proteins were analyzed for relation to reproductive traits including conception rate and days open. Associations between polymorphic systems and reproductive traits in 15 of 112 analyses were significant. The S blood system appeared most influential, having statistical significance in five of ten traits. These were conception rates in all services for female phenotypes, male phenotypes, and male by female phenotypes combined, conception rate in first services for female phenotypes, and probability of conception for female phenotypes. The FV system influenced conception rates in all services and in first services for male by female phenotypes combined. Four of the polymorphic systems had no effect on any of the reproductive traits. Maternal-fetal incompatibility was not evident from comparing parental combinations of aborted fetuses and normal calves. Conception rates declined with age of cow. For animals that ultimately conceived, conception rates did not decline consistently from first to later services within a service period.

Animals↗