Assortative mating and the genetic correlation

Summary The effect of assortative mating on the genetic correlation between traits X and Y is considered. Assortation on trait X changes the magnitude of the genetic correlation but not its sign. There are two situations depending on the signs of the correlation between mates () and of the random mating genetic correlation (): 1) if sign () = sign (), then >, where is the genetic correlation at equilibrium after continued assortation, and 2) if sign () = sign (), then < . However, negative assortative mating is virtually powerless to alter the magnitude of the genetic correlation. The consequences of a mixed assortation model, e.g., high milk production females mated to fast growing males and lesser productive females mated to slower growing sires, were also studied. Mixed positive assortation always increases the genetic correlation, but negative assortation decreases it. The implications of assortative mating on correlated responses to selection and on the equilibrium covariances between relatives for pairs of traits are discussed.     

Phosphorus depletion in the rhizosphere as influenced by soil moisture

To study the influence of soil moisture on phosphorus (P) depletion in the rhizosphere, maize (Zea mays cv. Trak) was pre-grown in vermiculite filled-PVC tubes for 9 days and then the plants with the tubes were transplanted into soil columns maintained at two soil moisture levels () of 0.14 and 0.20 cm³ cm^–3 for 10 days. The soil columns were separated at 1 cm depth by a nylon screen of 53 m inner mesh size, into 1 cm soil layer above and 3 cm soil column below screen. A root mat developed over the screen, but root hairs only could penetrate it. Regardless of the soil moisture level in the columns, and adequate and equal water and nutrients supply was maintained via wicks from an external nutrient solution to the plant roots in vermiculite. After 10 days, the soil columns were separated from the root mats, quickly frozen in liquid nitrogen and sliced into thin layers (0.2mm) using a refrigerated microtome to give soil samples at defined distances from the root mats for analyses. Lower soil moisture (=0.14) resulted in narrower and steeper depletion profile of 0.5 M NaHCO₃ extractable P (NaHCO₃-P_i) as compared to higher soil moisture (=0.20). Depletion of P in soil solution in the immediate vicinity of root mats did not differ much but the extension of the depletion zones was 0.10 cm at =0.14 and 0.20 cm at =0.20. The depletion up to 0.05cm with =0.14 and up to 0.07 cm with =0.20 was uniform, and may be attributed to the depletion in the root hair zone. Beyond the root hair zones, the theory of diffusion and mass flow was able to explain the observed differences in shape and extent of the P depletion profiles at the two soil moisture levels.     

Parametric and jackknife confidence interval estimators for two-factor mating design genetic variance ratios

Summary Confidence interval estimators have not been defined for dominance to additive genetic variance () and average degree of dominance () for the nested, factorial, and backcross mating designs. The objective of this paper was to describe interval estimators for these parameters. Approximate F random variables were defined for expected mean square (EMS) ratios for linear models with one environmental effect. Approximate 1– parametric interval estimators were defined for and using these random variables. Random variables defined for linear models with no environmental effects are not approximately distributed as F random variables because common EMS are involved in the numerators and denominators of the EMS ratios. Delete-one jackknife (jackknife) interval estimators were defined for and for linear models with zero or one environmental effect(s); In transformed analysis of variance point estimates were used in pseudovalue estimators.Oregon Agricultural Experiment Station Technical Paper No. 8067     

Spectral Characteristics of the EEG in Students with Different Levels of Result Achievement under the Conditions of Examination Stress

The EEG correlates of the performance of examination tests and special cognitive tests under the conditions of everyday study (common studying conditions, CSCs) and immediately before examination (examination conditions, ECs) were analyzed in 39 male students aged 18–20 years. The results of the examinations strongly correlated with the relative spectral power (SP) of the EEG rhythm before the examination. Therefore, the students were divided into two groups with different directions of changes in the -range SP under the ECs compared to the CSCs. Students from group 1 were characterized by increased relative - and -rhythm SPs under the ECs and a good examination performance; students of group 2, by decreased - and -rhythm SPs, an increased index of the EEG of the central and frontal cortical regions under the ECs, and a poor examination performance.     

The Duffy blood group is linked to the α-spectrin locus in a large pedigree with autosomal dominant inheritance of Charcot-Marie-Tooth disease type 1

Summary The -spectrin locus (SPTA) on chromsome 1 maps to 1q22–q25 and -spectrin specific probes detect restriction fragment length polymorphisms (RFLPs) with the endonucleases MspI and PvuII. The Duffy blood group (FY) has been mapped to the 1p21–q23 region. We found positive linkage between the -spectrin and the Duffy loci with a maximal Lod score of 3.81 at =0.0 using the computer program MLINK. This indicates that both loci are very closely linked and probably localized to 1q22–q23.     

Metabolism of a phenylcoumaran substructure lignin model compound in ligninolytic cultures of Phanerochaete chrysosporium

The degradation of the phenylcoumaran substructure model compound methyl dehydrodiconiferyl alcohol by the white-rot wood decay fungus Phanerochaete chrysosporium was investigated using culture conditions optimized for lignin oxidation. Initial attack was in the cinnamyl alcohol side chain, which was oxidized to a glycerol structure. This was subsequently converted by loss of the two terminal carbon atoms, C and C, to yield a C-aldehyde structure, which was further oxidized to the C-acid compound. The next detected intermediate, a phenylcoumarone, was produced by double bond formation between C and C, and oxidation of the C-alcohol to an aldehyde group. Further oxidation of C to an acid yielded the next intermediate. The final identified degradation product was veratric acid. No products from the 5-substituted aromatic ring, and no phenolic products, were found. The initial glycerol-containing intermediate was a mixture of the threo and erythro forms, and no optical activity could be found, suggesting that its formation might have involved nonstereospecific C-C epoxidation followed by non-enzymatic hydrolysis of the epoxide.Abbreviations TLC thin layer chromatography - LDA lithium diisopropyl amide - DDQ 2,3-dichloro-5,6-dicyanobenzoquinone - MS mass spectrometry - UV ultraviolet spectroscopy     

Peptide modification by incorporation ofα-trifluoromethyl substituted amino acids

Summary Metabolic stabilization of pharmacologically active peptides can be achieved by incorporation of sterically hindered non-natural amino acids, e.g. C ^, -disubstituted amino acids.-Trifluoromethyl substituted amino acids, a subclass of C ^, -disubstituted amino acids, also fulfil this requirement while featuring additional properties based on the electronic influence of the fluorine substituents.This review summarizes the results concerning the stability of peptides containing-TFM amino acids towards proteolysis by-chymotrypsin. Furthermore, configurational effects of-TFMAla on the proteolytic stability of peptides are explained using empirical force field calculations. The influence of-TFMAla incorporation on the secondary structure of selected tripeptide amides is compared to the effects exerted by its fluorine-free analogue, aminoisobutyric acid.Finally, results on metabolic stabilization and biological activity of modified thyrotropin releasing hormone are interpreted.     

A method for the investigation of those transformations under which the visual recognition of a given object is invariant

An experiment is described which shows in operation the program set out in Foster (1972a) for the investigation of the invariance transformations of visual recognition. The concern in the present study is with the Lie group of rotations SO(2), and a certain centrally located foveal Landolt ring. By presenting to the visual system this Landolt ring and a rotated image in rapid succession, one attempted to induce a specified rotation-type phi-motion. Two subjects were employed. Both reported the existence of the required type of phi-motion for rotations ₀ of the Landolt ring about the visual axis with -2/72/7. By appealing to the basic Proposition 2 of Foster (1972 a), the conclusion is reached that the visual system appears capable of effecting upon a certain centrally located foveal annulus the local 1-parameter group of rotations about the visual axis ₀, [–2/7,2/7].     

Order of bovine DRB3, DYA,and PRL determined by sperm typing

The order and recombination fractions () between the bovine major histocompatibility complex DRB3, DYA, and prolactin (PRL) genes were determined by typing of 254 sperm from a triply heterozygous bull. A recently developed method, primer extension preamplification (PEP), was used to amplify the bovine sperm genome prior to amplification of specific loci by the polymerase chain reaction (PCR). At least 28 copies of the DRB3, PRL, or DYA gene were obtained from 50 cycles of PEP. For sperm typing, alleles of each locus were discriminated by restriction endonuclease cleavage of PCR products and polyacrylamide gel electrophoresis of the restriction fragments. The most likely gene order is PRL-DRB3-DYA, with =0.025 (±0.012) and =0.150 (±0.024), respectively. The odds are 128:1 in favor of this order in comparison with the second most likely order DRB3-PRL-DYA. Our results demonstrate the power of sperm typing in concert with PEP for multilocus gene mapping.     

Methane production by anaerobic digestion of animal manures

Anaerobic digestion of swine manure was performed at mesophilic and thermophilic temperatures. In addition, the possibility of enhancement of biogas production by the co-digestion of manures with cellulosic waste residues (e.g., corn stover), was investigated. In the latter studies, the effect of particle size on the gasification efficiency was assessed.Methane productivity, G(m³ methane/m³ slurry volume.day), in the digesters operating at a stationary state could be correlated with the volatile solids loading, L (kg/m³.day), Retention time, (days), and pH as follows: G = L/(1 + 10^pK-pH) + [k/(1 + k)] where is dependent primarily on the nature of the utilizable carbohydrate fraction. The constant, , is found to be a function of the organic nitrogenous fraction of the manure. The constants pK and k (days^-1) are dependent on the temperature only.     

Mapping dominant markers using F2 matings

The development of efficient methods for amplifying random DNA sequences by the polymerase chain reaction has created the basis for mapping virtually unlimited numbers of mixed-phase dominant DNA markers in one population. Although dominant markers can be efficiently mapped using many different kinds of matings, recombination frequencies and locus orders are often mis-estimated from repulsion F₂ matings. The major problem with these matings, apart from excessive sampling errors of recombination frequency () estimates, is the bias of the maximum-likelihood estimator (MLE) of ( _ML). when the observed frequency of double-recessive phenotypes is 0 and the observed frequency of double-dominant phenotypes is less than 2/3 — the bias for those samples is — . We used simulation to estimate the mean bias of _ML. Mean bias is a function of n and and decreases as n increases. Valid maps of dominant markers can be built by using sub-sets of markers linked in coupling, thereby creating male and feamle coupling maps, as long as the maps are fairly dense (about 5 cM) — the sampling errors of increase as increases for coupling linkages and are equal to those for backcross matings when =0. The use of F₂ matings for mapping dominant markers is not necessarily proscribed because they yield twice as many useful markers as a backcross population, albeit in two maps, for the same number of DNA extractions and PCR assays; however, dominant markers can be more effeciently exploited by using doubled-haploid, recombinant-inbred, or other inbred populations.     

Absence of linkage between the serum cholinesterase (CHE1) and rhesus (RH) loci

Summary Twenty-two informative families were analyzed for the CHE1: RH linkage relationship. The total results exclude loose linkage until =0.28.     

Hydraulic model of a gas-lift bioreactor with flocculating yeast

The hydraulic model of a gas lift bioreactor, during a continuous alcoholic fermentation by using a strongly flocculating yeast, is analysed. Sucrose at two different concentrations (50 and 100 g/l) was used as substrate and the dilution rate for all the experiments was 1 h^–1. The biomass concentrations were between 85 and 110 g dry weight/1. A stimulus response technique was used to obtain the Residence Time Distribution curves, a pulse of a lactose solution being used as the tracer. Mixing time was determined by means of the response to a pulse of an acid tracer. These experiments were carried out by using an on-line data-acquisition system. The bioreactor behaviour is completely homogeneous, except for high substrate and biomass concentrations. A two parameters combined model is necessary, in this case, to fit the experimental data. Mixing times are very low, in the order of 10 seconds.List of Symbols C _T1 Tracer concentration of the tank 1 (g/l) - C _T10 Reference tracer concentration (g/l) - C Normalized tracer concentration (dimensionless) - Q ₀ Feed flowrate (l/h) - Q ₁ Flow exchanged between tank 1 and 2 (l/h) - [S] Substrate concentration (g/l) - t Time (s) - t _mix Mixing time (s) - t _c Circulation time (s) - V Reactor total volume (l) - X Biomass concentration expressed as dry weigh (g d.w./l) - Fraction of the total volume occupied by the highly agitated region - Fraction of the total flow which is exchanged between reactor 1 and 2 - Mean residence time (s), = V/Q ₀ - Dimensionless time, = t/ The stay of E. Roca at the ISIM in Montpellier (France) was supported by a grant from the CICYT (project BIO92 0568) of the Spanish Government.     

Linkage analyses of human peptidase C (PEPC), human factor H (HF), and coagulation factor XIIIB (F13B)

Summary Linkage data on human peptidase C (PEPC), human factor H (HF), and coagulation factor XIIIB (F13B) are presented. The results confirm linkage between HF and F13B (lod=5.32 at =0.10 in males), and give strong evidence for linkage between PEPC and HF (lod=5.14 at =0.10 in males) and between PEPC and F13B (lod=3.55 at =0.10 in males). The claim that PEPA is linked with HF must be withdrawn.     

Inheritance of mitochondrial DNA in lentil (Lens culinaris Medik.)

Restriction fragment analysis was used to examine the inheritance of lentil mitochondrial DNA (mtDNA) in F₁ and F₅ progeny from intrasubspecific (Lens culinaris ssp. culinaris) crosses and in F₁ progeny from intersubspecific (Lens culinaris ssp. orientalis x L. culinaris ssp. culinaris) crosses. Southern blots of digested parental and progeny DNA were hybridized to heterologous maize mtDNA probes specific to coxI and atp6 genes. Two restriction fragment polymorphisms separated L.c. ssp. culinaris Laird and Eston from L.c. ssp. culinaris ILL5588, and one restriction fragment polymorphism distinguished L.c. ssp. culinaris Laird and Eston from L.c. ssp. orientalis LO4. Twelve of 13 f₁ progeny and all F₅ progeny from the intrasubspecific crosses, and all F₁ progeny from intersubspecific crosses had only maternal mtDNA restriction fragments. One f₁ plant from an Eston x ILL5588 cross inherited mtDNA fragments from both parents. Nuclear DNA inheritance was biparental in all F₁ progeny.NRCC No. 38451     

α-Thalassemia and the production of different α chain variants in heterozygotes

The production of five chain variants (Hb G-Georgia, Hb St. Luke's, Hb Lloyd, Hb Montgomery, and Hb G-Philadelphia) in heterozygotes was evaluated through hematological observations, hemoglobin quantification, and biosynthetic studies. All heterozygotes for Hb St. Luke's and Hb Lloyd and most heterozygotes with Hb G-Georgia and Hb Montgomery had normal hematology and average / values of about 1.1. They were assigned a normal genotype (^G/), although the proportions of Hb St. Luke's and Hb G-Georgia were low (10 to 13%) and those of Hb Lloyd and Hb Montgomery twice as high (20%). Data from short-term incubations confirmed this genotype for some of these heterozygotes. Isolated Hb St. Luke's and Hb G-Georgia gave low ^G/ values (0.2 and 0.3) indicating that these Hb variants were defective at the level of Hb assembly. Isolated Hb Montgomery and Hb G-Philadelphia, however, gave higher ^G/ values of 0.6 and 0.8, respectively. A second type of variability existed among Hb G-Georgia (20 vs. 13%), Hb Montgomery (28 vs. 20%), and Hb G-Philadelphia (47 vs. 34%) heterozygotes, in whom the levels of Hb G differed. The occurrence of higher levels of these three chain heterozygosities was associated with hematological or biosynthetic evidence of a mild or moderate chain deficiency due to an -thalassemia-2 heterozygosity (^G/⁰ or ^0G/) or a homozygosity (^0G/⁰), respectively.This study was supported in part by USPHS Research Grants HLB-05168 and HLB-15158.     

Genetic linkage heterogeneity in the fragile X syndrome

Summary Genetic linkage between a factor IX DNA restriction fragment length polymorphism (RFLP) and the fragile X chromosome marker was analyzed in eight fragile X pedigrees and compared to eight previously reported pedigrees. A large pedigree with apparently full penetrance in all male members showed a high frequency of recombination. A lod score of-7.39 at =0 and a maximum score of 0.26 at =0.32 were calculated. A second large pedigree with a non-penetrant male showed tight linkage with a maximum lod score of 3.13 at =0, a result similar to one large pedigree with a nonpenetrant male previously reported. The differences in lod scores seen in these large pedigrees suggested there was genetic heterogeneity in linkage between families which appeared to relate to the presence of nonpenetrant males. The combined lod score for the three pedigrees with nonpenetrant males was 6.84 at 0=0. For the 13 other pedigrees without nonpenetrant males the combined lod score was-21.81 at =0, with a peak of 0.98 at =0.28. When lod scores from all 16 families were combined, the value was-15.14 at =0 and the overall maximum was 5.13 at =0.17.To determine whether genetic heterogeneity was present, three statistical tests for heterogeneity were employed. First, a predivided-sample test was used. The 16 pedigrees were divided into two classes, NP and P, based upon whether or not any nonpenetrant males were detected in the pedigree. This test gave evidence for significant genetic heterogencity whether the three large pedigrees with seven or more informative males (P<0.005), the eight pedigrees with three informative males (P<0.001), or all 16 pedigrees (P<0.001) were included in the analysis. Second, Morton's large sample test was employed. Significant heterogeneity was present when the analysis was restricted to the three large pedigrees (P<0.025), or to the eight pedigrees with informative males (P<0.05) but not when smaller, less informative pedigrees were also included. Third, an admixture test for heterogeneity was employed which tests for linkage versus no linkage. A trend toward significance was seen (0.05<P<0.10) which increased when the analysis was restricted to the larger, more informative pedigrees.The pedigrees where nonpenetrant males are detected appear to constitute one class (NP) where tight linkage to factor IX is predicted. The pedigrees where full penetrance is present appear to consitute a second class (P) where loose linkage to factor IX is predicted. Either the chromosomal location of the mutation or suppression of recombination to nearby genes may be different in the two classes of pedigrees. In the NP class of fra X pedigrees, information from DNA analysis should be useful for carrier detection, prenatal diagnosis, and genetic counseling.     

Multipoint linkage analysis in X-linked Alport syndrome

Summary In order to localize the gene for the X-linked form of Alport syndrome (ATS) more precisely, we performed restriction fragment length polymorphism analysis with nine different X-chromosomal DNA markers in 107 members of twelve Danish families segregating for classic ATS or progressive hereditary nephritis without deafness. Two-point linkage analysis confirmed close linkage to the markers DXS17(S21) (Z _max = 4.44 at = 0.04), DXS94(pXG-12) (Z _max=8.07 at =0.04), and DXS101(cX52.5) (Z _max=6.04 at =0.00), and revealed close linkage to two other markers: DXS88(pG3-1) (Z _max =6.36 at =0.00) and DXS11(p22–33) (z _max=3.45 at =0.00). Multipoint linkage analysis has mapped the gene to the region between the markers DXS17 and DXS94, closely linked to DXS101. By taking into account the consensus map and results from other studies, the most probable order of the loci is: DXYS1(pDP34)-DXS3(p19-2)-DXS17-(ATS, DXS101)-DXS94-DXS11-DXS42(p43-15)-DXS51(52A). DXS88 was found to be located between DXS17 and DXS42, but the order in relation to the ATS locus and the other markers used in this study could not be determined.     

The measurement of mean temperatures in plant and soil studies by the sucrose inversion method

Summary A polarimetric procedure is described for determining exponential mean temperatures (_e) from the rate of inversion of sucrose solutions buffered at pH values between 1 and 3. An equation is given for calculating the pH values appropriate for various temperature ranges and time scales. The procedure used for monitoring air and soil temperatures over a 5 year period at a network of sites in Aberdeenshire was to expose 5 ml volumes of sucrose solution at pH 2.06 in sealed polythene tubes. Each month the changes in optical rotation were measured with a sensitive automatic polarimeter and fresh tubes exposed. The values of _e were 2°C higher than arithmetic means obtained from standard thermometric devices. Observations at elevations between 275 and 686 m a.s.l. demonstrate the lapse of temperature with altitude and illustrate the usefulness of _e measurements.     

Asymmetries in population growth regulated by intraspecific competition: Empirical studies and model tests

Summary The linearity assumption in the logistic model of population growth is violated for nearly all organisms. Two simple models, the -logistic and the -Ricker, are shown to account for asymmetric patterns of population growth for 27 species of Drosophila and for a variety of other organisms, where the data were derived from the literature. These models are developed so as to aid laboratory and field ecologists to anticipate the dynamics of various experimental organisms. Potential problems of data gathering and model applications for experimental ecologists and wild life management biologists are identified. Intraspecific asymmetries offer alternative explanations to the habitat selection model, and the higher order interactions or coalitions model, for interspecific competition.