The distribution of endogenous virus (ev) genes was studied in five commercial layer lines; four were brown-egg types and one was White Leghorn. The DNA samples were obtained from nine birds of each line and digested with SacI and BamHI endonucleases. The DNA fragments were separated by gel electrophoresis, and Southern blots were prepared and examined for the presence of ev genes following hybridization with the labeled recombinant plasmid pRAV-2 and autoradiography. Almost all fragments were present in more than one line, suggesting that each line has drawn a random assortment of ev genes from the same common pool, possibly as a founder effect. A great degree of polymorphism is shown by the ev genes in the lines investigated. Most fragments were present at low or intermediate frequencies. Very few fragments were present in only one line or in only one bird. This suggests that de novo integration of ev genes at new sites is a relatively rare event. Very few fragments were present at high frequencies, and none of the fragments, except for the BamHI internal fragments, were present in all birds of all lines. Considering that ev genes are present in the wild progenitor of the domestic chicken, the lack of fixation of any ev genes in the chicken genome is remarkable. It is proposed that ev genes have general deleterious effects in the chicken (hence, the lack of fixation), but those ev genes that have been retained in the chicken genome have favorable effects under some circumstances with consequent equilibrium at low to intermediate frequencies. It is speculated that the retained ev genes may represent sites of favorable mutation via insertional mutagenesis and, hence, a potential route to the cloning of genes of economic importance in poultry.

Analysis of Variance↗

PubMed1991

Selection for high and low threshold body weight at first egg in broiler strain females. 1. Direct response to selection and correlated effects on juvenile growth rate and age at first egg.

A selection program for high and low threshold body weight at first egg was carried out in a broiler line. Selection was on the basis of weight at first egg, following gradual release from feed restriction at a relatively advanced age. After six generations of selection, the lines differed by 862 g in the trait under selection. In addition, 6-wk body weight of high-line (HL) birds was 91 g greater, and age at first egg was 32 days greater than in low-line (LL) birds. When raised under an ad libitum feeding regimen from hatch, HL birds entered lay 20 days later than LL birds. When onset of lay was markedly delayed by maintaining feed restriction until 29 wk of age, body weight at first egg of HL birds was greater by 645 g than that of LL birds. Similarly, when birds of the two lines were subjected to forced molt and brought to a body weight well below that of initial body weight at first egg, and then allowed to gain weight and reenter lay, body weight difference at first egg of HL and LL birds following rehabilitation was similar to that found on original entry into lay. It is proposed that the results may most plausibly be explained as resulting from a primary effect of the selection procedure on the time required to first egg from onset of sexual competence, defined as onset of responsiveness to lay-inducing factors such as light. Alternative explanations involve effects of the selection procedure on threshold weight or threshold age requirements for sexual competence.

Animal Feed↗

PubMed1991

Two-way selection for threshold body weight at first egg in broiler strain females. 2. Effect of supplemental light on weight and age at first egg.

In order to undergo the processes leading to lay, female chickens must reach a minimum threshold age and body weight, and be exposed to some minimum amount of light stimulation. By two-way selection over six generations lines were developed that differed markedly in body weight at first egg. The effect of supplemental light on age and body weight at first egg of these lines was studied in two experiments. In the first experiment, birds of the two lines were provided ad libitum access to feed from hatch, reaching the weight threshold at an early age. Supplemental light was provided at either 91 or at 126 days of age (before or after the age threshold, respectively). Differences in body weight and age at first egg of the two lines were the same in both light treatments. In the second experiment, birds of the two lines were raised under feed restriction to 154 days of age and then released to ad libitum feeding under supplemental or natural (autumn) light. Differences between the lines in age and weight at first egg were greater in the group maintained under natural light than under supplemental light. The results are interpreted in terms of a model relating age at first egg to weight and age thresholds for onset of competence to respond to light stimulation, and to cumulative light stimulation required from onset of competence to first egg. It is proposed that selection affected the total amount of light stimulation required from onset of competence to onset of lay, but did not affect weight or age thresholds for onset of competence.

Aging↗

PubMed1990

Large restriction fragments containing poly-TG are highly polymorphic in a variety of vertebrates.

Southern blots of genomic DNA from a variety of species digested by restriction endonucleases having a four-bp specificity, were probed with a bovine genomic clone consisting of seven tandem poly-TG stretches separated by a 29bp linker sequence. Highly variable DNA 'fingerprint' patterns were obtained in chicken, sheep, and horse, moderately variable DNA 'fingerprints' in mouse and man, and a monomorphic pattern in Drosophila. In chicken, horse and man a (TG)10 synthetic oligonucleotide probe gave results identical to those given by the bovine probe. Furthermore, in chicken the DNA fingerprint variation showed typical Mendelian inheritance and differed from the fingerprints obtained with Jeffreys 33.6 and M13 minisatellite probes. Thus, for a variety of vertebrate species, poly-TG-containing probes can uncover useful genetic variation.

Animals↗

PubMed1990

(TG)n uncovers a sex-specific hybridization pattern in cattle.

Screening of a bovine genomic library with the human minisatellite 33.6 probe uncovered a family of clones that, when used to probe Southern blots of bovine genomic DNA digested with the restriction enzyme HaeIII or MboI, revealed sexually dimorphic, but otherwise virtually monomorphic, patterns among the larger DNA fragments to which they hybridized. Characterization of one of these clones revealed that it contains different minisatellite sequences. The sexual dimorphism hybridization pattern observed with this clone was found to be due to multiple copies of two tandemly interspersed repeats: the simple sequence (TG)n and a previously undescribed 29-bp sequence. Both repeats appear to share many genomic loci including autosomal loci. In contrast, Southern analysis of AluI- or HinfI-digested bovine DNA with the (TG)n repeat used as a probe yielded substantial polymorphism. These results show that (i) different minisatellites can be found in a cluster, (ii) both simple and more complex repeated sequences other than the simple quaternary (GATA)n repeat can be sexually dimorphic, and (iii) simple repeats can reveal substantial polymorphism.

Animals↗

PubMed1990

Toward a unified approach to genetic mapping of eukaryotes based on sequence tagged microsatellite sites.

The genomes of all eukaryotes appear to contain a special class of loci, termed microsatellites, which can serve, if sequenced and taken as the substrate for the polymerase chain reaction, as highly informative, locus-specific markers. By analogy to the "sequence tagged sites" recently proposed by Olsen et al. for standardizing the human physical gene map, these microsatellite markers are termed "sequence tagged microsatellite sites" (STMS). Genetic maps based on STMS will share with the Olsen physical maps the advantage that mapping vocabularies will be standardized to the DNA sequence base and that access to any particular locus will not require shipping or storing cloned probes. The species map will consist simply of a listing of nucleotide sequences. Reference populations for developing STMS maps can be chosen on the basis of biological or economic interest. It will not be necessary to maximize for genetic divergence.

Animals↗

PubMed1978

Testicular testosterone biosynthesis in male Saanen goats with XX sex chromosomes.

Explore the source record for details and available documents.

Androstenedione↗

PubMed1976

Genetic and environmental correlations between brain weight and maze learning in inbred strains of mice and their F1 hybrids.

The relationships among body weight, cerebellum weight, cerebrum weight, maze-learning ability in a double T-maze, and discrimination learning in a Y-maze were studied in six inbred strains of mice and some of their F1 hybrids. The subjects were 131 male albino mice from 14 genotypic groups: five inbred groups and nine groups of crossbred offspring. Intra- and intergroup correlations were computed between all possible pairs of the anatomical and behavioral traits. A significant difference between the intragroup and intergroup correlations for any pair of variables was taken to indicate the presence of a genetic correlation between the two variables. On this basis, positive genetic correlations were indicated between T-maze learning ability and Y-maze learning ability, between body weight and T-maze learning ability, and possibility between body weight and both cerebellum and cerebrum weight and between cerebrum weight and T-maze learning ability. Negative genetic correlations were indicated between cerebellum weight and running time in both mazes and between total number of successes in the Y-maze and Y-maze running time.

Animals↗

PubMed1975

A note on assortative mating and artificial selection.

A simple method is presented for determining the effect on the genetic variance of a quantitative trait, of selection followed by various degrees of assortative mating.

Animals↗

PubMedDate not supplied

Familial differences in antibody response of broiler chickens to vaccination with attenuated and inactivated Newcastle disease virus vaccine.

Genetic differences in immune response to Newcastle disease virus (NDV) were studied in 4-week-old broilers, vaccinated with attenuated (live) or inactivated NDV. The experiment included 370 chicks from two farms distributed among 22 sire families and 60 dam families. Results in chicks from both farms were similar. Survival after challenge was closely related to titer level. The genetic correlation between day-7 and day-12 titers (attenuated virus) was 1.0. Significant differences were found between sire families in both sorts of vaccinations. Heritabilities based on the sire variance components for attenuated and inactivated virus vaccinations were respectively 0.31 and 0.60. The genetic correlation between them was 0.49. Nevertheless, it is concluded that selection for response to NDV based on inactivated virus may be most effective in improving response to attenuated NDV vaccinations.

Animals↗