How Did Domestication Change the Hair Morphology in Sheep and Goats?

We analysed macro-and microscopic features of dorsal guard hairs in 21 specimens of wild and domestic sheep and goats. We integrated and extended the available data on hair morphology of wild species and provide a first comparative analysis of hair structure of domestic forms. Domestic sheep and goats, probably due to a convergence process under artificial selection, show similar medullary features to each other and different medullary structures from their relative wild relatives. Different breeds show a diverse alteration of the medullary structure probably correlated to the duration of the domestication process. Domestic sheep have a cuticular structure different from the relative wild ancestor, while domestic goats do not show clear differences in the cuticle from the related wild species. The strong artificial selection for wool production may have transformed the hair structure of the sheep, but not that of the goat. We described the effects of age on the microscopic structure of hair, which have not yet been investigated. The medullary structure and the cuticular pattern in domestic forms do not change with age, as seen in wild species, because juveniles characters are retained in adults due to domestication.     

Genetic Prediction: What are the Limits?

The spectre of determinism stalks many of the concerns surrounding the impact of genetic research into both disease and normal behaviour. The ability accurately to predict a person's actions would certainly have profound implications for notions of individuality and free will. But to what extent will the current explosion in genetic research provide more accurate predictors than have been available for millennia in the form of wealth, social status and perceived family resemblance? The genetic research program is at too early a stage to answer this question with confidence, but various indicators tend to point in the same direction: the predictive ability of genetic analysis will generally be low. This conclusion runs counter to widely perceived popular notions. The deconstruction of genetic determinism is an essential safeguard against the real concern that genetic information may be used for discrimination by unscrupulous powers.     

Genetic Variation in Toxicant-Stressed Populations: An Evaluation of the “Genetic Erosion” Hypothesis

The question whether environmental pollution affects genetic diversity in natural populations remains unanswered to date despite the fact that genetic variation is one of the three pillars of biodiversity recognized in the Rio convention of 1993. The loss of genetic diversity in populations subjected to anthropogenic stress can be designated as “genetic erosion” and may be considered as a factor of concern in risk assessment of toxic chemicals. Theoretically there are four different ways in which toxicants can affect genetic variation: (i) by increasing mutation rates, (ii) by directional selection on tolerant genotypes, (iii) by causing bottleneck events, and (iv) by altering migration. This paper reviews studies that have documented genetic change in animal populations exposed to environmental pollution. In these studies, genetic variation is measured in a variety of ways: heritability of quantitative characters, heterozygosity of allozyme loci, haplotype diversity in mitochondrial DNA, and variability in RAPD fingerprints. Studies on cadmium tolerance of Collembola living in metal-contaminated soil suggest that strong directional selection pressure may decrease genetic variability of traits immediately linked to tolerance. Allozyme studies in fish have documented a similar decrease of genetic variation in populations living in strongly acidified waters. A correlation between RAPD-PCR-based genetic similarity and site contamination has been documented in crayfish. Overall, there is significant support for the genetic erosion hypothesis, but the issue cannot be considered settled. In most studies insufficient attention is given to factors such as population size, bottlenecks and mutation, which may influence genetic variability in addition to the toxicant selection regime. At the moment, there does not seem to be a sound scientific basis for incorporating genetic diversity measurements into risk assessment, despite the variety of easily applicable molecular techniques available. It is often not known what kind of variation is measured by these techniques (neutral or selectable) and how the markers are inherited. Given the importance of the issue, as stressed by the Rio Convention, a concentrated research effort is necessary to better define the question and find a general approach to evaluate its importance in ecological risk assessment.     

Genetic Characterization of the Drosophila Birt-Hogg-Dubé Syndrome Gene

Folliculin (FLCN) is a conserved tumor suppressor gene whose loss is associated with the human Birt-Hogg-Dubé (BHD) syndrome. However, its molecular functions remain largely unknown. In this work, we generated a Drosophila BHD model through genomic deletion of the FLCN gene (DBHD⁻). The DBHD mutant larvae grew slowly and stopped development before pupation, displaying various characteristics of malnutrition. We found the growth delay was sensitive to the nutrient supplies. It became more severe upon restrictions of the dietary yeast; while high levels of yeast significantly restored the normal growth, but not viability. We further demonstrated that leucine was able to substitute for yeast to provide similar rescues. Moreover, the human FLCN could partially rescue the DBHD⁻ phenotypes, indicating the two genes are involved in certain common mechanisms. Our work provides a new animal model of the BHD syndrome and suggests that modulation of the local nutrient condition might be a potential treatment of the BHD lesions.     

Genetic Analysis of the Bacteriophage λ Attl Nucleoprotein Complex

Site-specific recombination in bacteriophage λ involves interactions among proteins required for integration and excision of DNA molecules. We have analyzed the elements required to form an in vivo nucleoprotein complex of integrase (Int) and integration host factor (IHF). Interaction of Int with the core (the site of strand exchange) is stabilized by the flanking arm region of attL. IHF, in addition to Int, is required for efficient Int-core binding. We used the in vivo attL binding assay to characterize several Int variants for their abilities to form stable attL complexes. Substitution of Int active site tyrosine 342 by phenylalanine had no effect on the ability of the protein to form attL complexes. Three other amino acids that are completely conserved in the integrase family of recombinases (arginine 212, histidine 308, and arginine 311) were separately substituted by glutamine, leucine, and histidine, respectively. In each case, the mutant protein was altered in its ability to form attL complexes while retaining its ability to bind to the λ arm-type sites. We propose that, in addition to their role in catalysis, this triad of amino acids helps the Int protein to interact with the λ core sites.     

Does the Genetic Code Have A Eukaryotic Origin?

In the RNA world, RNA is assumed to be the dominant macromolecule performing most, if not all, core "house-keeping" functions. The ribo-cell hypothesis suggests that the genetic code and the translation machinery may both be born of the RNA world, and the introduction of DNA to ribo-cells may take over the informational role of RNA gradually, such as a mature set of genetic code and mechanism enabling stable inheritance of sequence and its variation. In this context, we modeled the genetic code in two content variables-GC and purine contents-of protein-coding sequences and measured the purine content sensitivities for each codon when the sensitivity (% usage) is plotted as a function of GC content variation. The analysis leads to a new pattern-the symmetric pattern-where the sensitivity of purine content variation shows diagonally symmetry in the codon table more significantly in the two GC content invariable quarters in addition to the two existing patterns where the table is divided into either four GC content sensitivity quarters or two amino acid diversity halves. The most insensitive codon sets are GUN (valine) and CAN (CAR for asparagine and CAY for aspartic acid) and the most biased amino acid is valine (always over-estimated) followed by alanine (always under-estimated). The unique position of valine and its codons suggests its key roles in the final recruitment of the complete codon set of the canonical table. The distinct choice may only be attributable to sequence signatures or signals of splice sites for spliceosomal introns shared by all extant eukaryotes.     

Genetic Features of the Tomato Marker Line Мо938

Russian Journal of Genetics - In cultivated tomato hybrids (Marglobe × Mo938), the anthocyanin-free gene shows linked inheritance with the d (dwarf) gene on chromosome 2, but with a...     

Genetic linkage studies of the human glycosphingolipid β-galactosidases

The genetic linkage relationships of the human glycosphingolipid beta-galactosidases were determined using human--mouse somatic cell hybrids. A new method was devised for the estimation of human galactosylceramide, lactosylceramide, and GMI-ganglioside beta-galactosidase activities in the presence of their mouse counterparts, which takes advantage of the reproducible specific activity of lysosomal hydrolases under a given set of culture conditions and is based on differences in both pH optima and sensitivity to chloride ion. Human and mouse chromosomes were identified by their characteristic banding patterns obtained after quinacrine staining, and the optimum glycolipid beta-galactosidase activity was determined for three different substrates. A ratio was defined for each activity which was the specific activity at the human pH optimum divided by the specific activity at the mouse pH optimum. Linear regression analysis was used to test for concordant segregation between pH ratios for each enzyme and the frequency of occurrence of different human chromosomes in the man--mouse somatic hybrid clones. The results obtained from two independent series of hybrid clones indicated that human beta-galactosidase activities consistently segregated with human chromosome 12 in these somatic cell hybrids.     

Is the Genetic Code Optimized for Resource Conservation?

The causes and consequences of the nonrandom structure of the standard genetic code (SGC) have been of long-standing interest. A recent study reported that mutations in present-day protein-coding sequences are less likely to increase proteomic nitrogen and carbon uses under the SGC than under random genetic codes, concluding that the SGC has been selectively optimized for resource conservation. If true, this finding might offer important information on the environment in which the SGC and some of the earliest life forms evolved. However, we here show that the hypothesis of optimization of a genetic code for resource conservation is theoretically untenable. We discover that the aforementioned study estimated the expected mutational effect by inappropriately excluding mutations lowering resource consumptions and including mutations involving stop codons. After remedying these problems, we find no evidence that the SGC is optimized for nitrogen or carbon conservation.     

Genetic studies on the β-amylase isozymes of barley malt

From genetic studies on two -amylase forms (Sd1 and Sd2) observed in barley malts it is concluded that the Sd1 and Sd2 phenotypes are controlled by a pair of alleles acting without dominance. Gene dosage effects typical of characters determined by the endosperm were observed in F₁ hybrids, Preliminary studies on the distribution of Sd1 and Sd2 forms indicate that Sd1 is the rarer one; of thirty-one cultivars tested, twenty were Sd2, nine were typed as Sd1 and two cultivars had both Sd1 and Sd2 phenotypes. An analysis of joint segregations for Sd1, Sd2, the heat-stable -amylases and two esterase forms gave no evidence for linkage between these three loci.     

Mechanism for the Action of λ Exonuclease in Genetic Recombination

Lambda exonuclease degrades in vitro redundant single stranded regions which probably result in λ DNA from genetic recombination in vivo.     

Genetic Modification of the Soybean to Enhance the β-Carotene Content through Seed-Specific Expression

The carotenoid biosynthetic pathway was genetically manipulated using the recombinant PAC (Phytoene synthase-2A-Carotene desaturase) gene in Korean soybean (Glycine max L. cv. Kwangan). The PAC gene was linked to either the β-conglycinin (β) or CaMV-35S (35S) promoter to generate β-PAC and 35S-PAC constructs, respectively. A total of 37 transgenic lines (19 for β-PAC and 18 for 35S-PAC) were obtained through Agrobacterium-mediated transformation using the modified half-seed method. The multi-copy insertion of the transgene was determined by genomic Southern blot analysis. Four lines for β-PAC were selected by visual inspection to confirm an orange endosperm, which was not found in the seeds of the 35S-PAC lines. The strong expression of PAC gene was detected in the seeds of the β-PAC lines and in the leaves of the 35S-PAC lines by RT-PCR and qRT-PCR analyses, suggesting that these two different promoters function distinctively. HPLC analysis of the seeds and leaves of the T₂ generation plants revealed that the best line among the β-PAC transgenic seeds accumulated 146 µg/g of total carotenoids (approximately 62-fold higher than non-transgenic seeds), of which 112 µg/g (77%) was β-carotene. In contrast, the level and composition of the leaf carotenoids showed little difference between transgenic and non-transgenic soybean plants. We have therefore demonstrated the production of a high β-carotene soybean through the seed-specific overexpression of two carotenoid biosynthetic genes, Capsicum phytoene synthase and Pantoea carotene desaturase. This nutritional enhancement of soybean seeds through the elevation of the provitamin A content to produce biofortified food may have practical health benefits in the future in both humans and livestock.     

Genetic control of “natural” killer lymphocytes in the mouse

Spleens from normal young mice contain lymphocytes that can kill certain in vitro grown Moloney lymphoma lines in a⁵¹Cr-release cytotoxicity test. A lymphoid cell without detectable T- or B-cell markers was previously shown to be responsible. Killing activity shows a marked dependence on the genotype of the donor mouse. When tested against a YAC line of strain A origin maintained in vitro spleens of A, A.CA, and A.SW mice had low activity, whereas CBA, C3H, C57L, and C57Bl spleens were highly active. In semisyngeneic F₁ crosses with strain A as one parent, reactivity resembled the opposite parental strain. Thus, (A×CBA)F₁, (A×C3H)F₁, (A×C57L)F₁, and (A×C57Bl)F₁ were reactive, whereas A×A.CA showed no significant activity. Analysis of the reactivity in (A×C57Bl)F₁×A backcross mice suggests that multiple genes are involved. Preliminary linkage analysis suggests at least oneH-2 linked factor. Another gene appears to be linked to theB (black) locus.     

RAPD–PCR Analysis of Genetic Diversity in the Manchurian Pheasant

The genetic diversity of a local population of the Manchurian pheasant Phasianus colchicus pallasi was studied using RAPD–PCR. Based on the DNA patterns obtained in PCR with five arbitrary decanucleotide primers, we assessed genetic polymorphism of this population, estimated genetic distances between individuals, and constructed an NJ phylogenetic tree, and an UPGMA dendrogram of genetic similarity. The population was shown to exhibit high average genetic polymorphism (P = 79.4%) and genetic distances (D = 0.267). Possible reasons for the high genetic diversity of this local population are discussed.     

Genetic parameters and genetic trends in the Chinese × European Tiameslan composite pig line. I. Genetic parameters

Genetic parameters of body weight at 4 (W4 w), 8 (W8 w) and 22 (W22 w) weeks of age, days from 20 to 100 kg (DT), average backfat thickness at 100 kg (ABT), teat number (TEAT), number of good teats (GTEAT), total number of piglets born (TNB), born alive (NBA) and weaned (NW) per litter, and birth to weaning survival rate (SURV) were estimated in the Chinese × European Tiameslan composite line using restricted maximum likelihood methodology applied to a multiple trait animal model. Performance data from a total of 4 881 males and 4 799 females from 1 341 litters were analysed. Different models were fitted to the data in order to estimate the importance of maternal effects on production traits, as well as genetic correlations between male and female performance. The results showed the existence of significant maternal effects on W4w, W8w and ABT and of variance heterogeneity between sexes for W22w, DT, ABT and GTEAT. Genetic correlations between sexes were 0.79, 0.71 and 0.82, respectively, for W22w, DT and ABT and above 0.90 for the other traits. Heritability estimates were larger than (ABT and TEAT) or similar to (other traits) average literature values. Some genetic antagonism was evidenced between production traits, particularly W4w, W8w and ABT, and reproductive traits.     

Genetic relationship between β-galactosidase and β-fucosidase in the mouse

Evidence for the identity of β-galactosidase and β-fucosidase enzymes in the house mouse was obtained by examination of the enzyme activities in animals from different crosses between C57BL/Kl mice with high galactosidase and fucosidase activities and DBA/2/Kl mice with low activities. There is a strong correlation between the activities of these two enzymes in different tissues of F₂ animals. A comparison of the fractionation properties of β-galactosidase and β-fucosidase showed that the two activities had a parallel distribution and identical thermostability. These data suggest that the same enzyme catalyzes the hydrolysis of both substrates.     

Genetic conflict outweighs heterogametic incompatibility in the mouse hybrid zone?

Background  

The Mus musculus musculus/M. m. domesticus contact zone in Europe is characterised by sharp frequency discontinuities for sex chromosome markers at the centre of wider clines in allozyme frequencies.