bluuebunny/crossref_metadata_2025 huggingface dataset:
The ecological genetics of growth in Drosophila 8. Adaptation to a New Diet
Authors: Robertson Forbes W.
Published: September 2009

1. Populations of Drosophila melanogaster have been adapted to a new, initially unfavourable diet by adding to the food medium the chelating agent, EDTA, which lowers survival, lengthens development and reduces body size, according to the concentration.

2. Six populations were allowed to adapt to the new diet without intervention and compared with two additional populations in which there was either artificial selection for fast development time or in which the effects of variation in development time were minimized and higher egg production was favoured instead.

3. All populations adapted successfully and some were able to grow on medium with EDTA concentrations which were lethal for the original population.

4. Under uncrowded conditions on EDTA-free medium, in seven out of the eight populations, body size was reduced by about 7% below the level of the original population and the larval period was shorter in several instances. But in the population in which higher egg production was favoured, body size was 7% greater than in the original population and 16% greater than the average of the other EDTA-adapted populations. This contrast was attributed either to intense natural selection for shorter development time or to selection for a higher rate of egg production, which is positively correlated with body size when larvae are grown on sub-optimal conditions.

5. Under crowded, competitive conditions, the fitness of the EDTA-adapted and the original populations was reversed according to the presence or absence of EDTA.

6. Genetic differences between one of the EDTA-adapted populations and the original population were studied by using marked inversions to interchange chromosome pairs. Larvae of the alternative genotypes were grown on different diets and adaptation was shown to have involved changes in all major chromosomes and also substantial, complementary interaction between non-homologous pairs. Substitution of the third pair of chromosomes from the original Pacific stock in the background of the adapted strain led to complete sterility of females, on all diets tested, and lethality of both sexes at higher levels of EDTA.

7. The creation of new equilibria, by manipulating the relative importance of components of fitness, in the course of adaptation to a new environment, offers a valuable technique for studying the selective forces which influence the mean value of quantitative characters generally.
Colicin resistance associated with resistance factors inEscherichia coli
Authors: Siccardi A. G.
Published: September 2009

Derivatives ofE. coliK12 which had received a number of different drug resistance factors by conjugation fromSalmonellastrains were found also to have acquired insensitivity to colicins. The insensitivity associated with some R factors was similar in character to immunity conferred by colicinogeny, while that given by others more closely resembled the higher level of resistance due to absence of the colicin receptor. It was, however, not complete. Many of the R factors also restricted the growth of various phages.
The location of Cattanach's translocation in the X-chromosome linkage map of the mouse
Authors: Cattanach B. M.
Published: September 2009

In Cattanach's X-autosome translocation a piece of autosome of linkage group I has been inserted into the X-chromosome and a piece of X may have been reciprocally translocated to the autosome (Cattanach, 1961; Ohno & Cattanach, 1962). The present communication reports investigations to locate the autosomal insertion in the X-chromosome linkage map and provide evidence pertinent to the question of the possible reciprocal nature of the rearrangement; a brief summary of the results has already been reported (Cattanach & Isaacson, 1965).
‘Nude’, a new hairless gene with pleiotropic effects in the mouse
Authors: Flanagan S. P.
Published: September 2009

1. Nude is a new recessive gene causing hairlessness in the mouse. It is linked to rex and trembler in linkage group VII. The order of the three loci and the recombination frequencies are as follows:

2. In addition to hairlessness the new gene causes reduced body growth rate, very low fertility and a liver disease causing death. Nude mice may be classified at birth by the absence of vibrissae.

3. The hairlessness is due to abnormal keratinization of hair in the follicles. The skin histology resembles that of naked mice. The hair follicles were found to be deficient in free sulphydryl groups.

4. The majority of nude mice die of general body weakness within 2 weeks of birth. The survivors grow slowly and may live for a considerable period. But all nude mice eventually die, usually between 3 and 14 weeks of age.

5. The livers of dead or moribund nude mice are covered with lesions and scars. The defect has been traced histologically to its initial stage, namely, necrosis of small areas of tissue.

6. Attempts to relate the deficiency of sulphydryl groups in the hair follicles to abnormal sulphur metabolism in the liver were unsuccessful.

7. Pseudo-cysts of a parasitic protozoan,Toxoplasma gondii, were identified in the liver and brain of nude mice. In one case the free form of the organism was found.

8. The possible relationship between the liver disease and the pathogenic organism is discussed.
Oocyte pachytene analysis of Cattanach's fd translocation
Authors: Slizynski B. M.
Published: September 2009

Oocyte pachytene analysis of embryos heterozygous for the fd translocation confirmed the facts of this translocation as described by Ohno and Cattanach. Besides that it revealed that a small piece of the X-chromosome has been transferred to the autosome where in about 25% of cases it shows less stainable expansion.
On the evolutionary adjustment of spontaneous mutation rates
Authors: Kimura Motoo
Published: September 2009

Evolutionary factors which tend to decrease the mutation rate through natural selection and those which tend to increase the mutation rate are discussed from the standpoint of population genetics. The author's theory of optimum mutation rate based on the principle of minimum genetic load is re-examined, assuming that mutation rate is adjusted in the course of evolution in such a way that the sum of mutational and substitutional load is minimized. Another hypothesis is also examined that only selection toward lowering the mutation rate is effective and the present mutation rate in each organism represents the physical or physiological limit that may be attained by natural selection.

The possibility cannot be excluded that the spontaneous mutation rate is near the minimum that may be attained under the present mode of organization of the genetic material, and at the same time is not very far from the optimum in the sense of minimizing the genetic load.
The limits to artificial selection for body weight in the mouse: III. Selection from crosses between previously selected lines
Authors: Roberts R. C.
Published: September 2009

1. Four lines selected for large size were crossed to form a base population for further selection for high 6-week weight; three small lines were crossed similarly, and the crossbred population was selected for low 6-week weight.

2. In every case, a cross between two selected lines resulted in heterosis increasing body weight. This shows that all of the selected lines were differentiated with respect to genes affecting body weight.

3. Further selection for large size produced a stock whose mean weight was 25% higher than the largest of the original lines at its limit. But the response to selection for small size was slow, and after twenty-four generations of selection, the low weights of two of the original lines had not been recovered.

4. The evidence points to linkage of genes affecting body weight in the mouse. It is suggested that this is a particular feature of crosses between previously selected lines, rather than a general feature of mouse populations.
The limits to artificial selection for body weight in the mouse: IV. Sources of new genetic variance—irradiation and outcrossing
Authors: Roberts R. C.
Published: September 2009

1. Two methods are examined of introducing new genetic variance into a line of mice selected for high 6-week weight which, at its limit, displayed no additive genetic variance.

2. The first method—irradiation—gave largely negative results. Any further gain under selection that was achieved could not be clearly distinguished from a possible environmental trend.

3. The second method—outcrossing to an unselected strain and then selecting from the cross—resulted in a clear gain over the original limit, but nine generations were required even to recover the original limit.

4. Various methods of transcending selection limits are evaluated in terms of their application to livestock improvement.
Close linkage between genes which cause hairlessness in the mouse
Authors: Flanagan S. P. , Isaacson J. H.
Published: September 2009

1. A new semi-dominant gene called shaven (Sha) causes hairlessness in the mouse and it is closely linked to naked. Homozygous shaven mice never grow a first coat and adults grow a few short hairs only. Shaven heterozygotes grow a full coat which is greasy.

2. The percentage recombination between shaven and naked was found to be 0·8%. Three-point tests with naked and caracul showed that the order of the three loci is either N–Sha–Ca or N–Ca–Sha.

3. The failure of homozygous shaven mice to grow a coat is due to abnormal keratinization of the hairs in the follicles. The follicles were found to be deficient in sulphydryl groups.

4. The greasiness of the Sha+ coat is due to the presence of a sudanophilic fluid in the hair medullae.

5. The close linkage between the two genes with similar phenotypic effects is discussed.
The addition of the chromosomes of Aegilops umbellulata to Triticum aestivum (var. Chinese Spring)
Authors: Kimber Gordon
Published: September 2009

Six lines have been isolated in which individual chromosomes of Ae. umbellulata have been added to the normal complement of T. aestivum. The phenotype and cytology of these lines and of the material employed in their production is briefly described. The use of some of these lines in investigations on the evolution of the diploid Aegilops species and in the introduction of useful alien variation into T. aestivum is mentioned.
Disruptive selection on sternopleural chaeta number in Drosophila melanogaster
Authors: Scharloo W. , Boer M. Den , Hoogmoed M. S.
Published: September 2009

It is generally accepted that reproductive isolation leading to the irreversible division of a Mendelian population into two species must be initiated during a period of geographical isolation (see Mayr, 1963). Thoday & Gibson (1962, Gibson & Thoday, 1963) obtained partial isolation within a population of Drosophila melanogaster by artificial disruptive selection for the number of sternopleural chaetae. This occurred in two experiments from the same base population after seven and twelve generations respectively. On the strength of these results they concluded that speciation does not require geographical isolation and that sympatric speciation by disruptive selection in a heterogeneous habitat is at least a theoretical possibility.
The properties of a temperate bacteriophage Wφ isolated fromEscherichia colistrain W
Authors: Glover S. W. , Kerszman G.
Published: September 2009

Escherichia colistrain W was found to be lysogenic for a temperate phage Wφ. This phage, which plates onE. coliC, forms λ-like plaques 2–3 mm. diameter with turbid centres. It is serologically unrelated to λ but is closely related to P2 which it resembles in the electron microscope. Its buoyant density in CsCl has been measured and it is different from λ but similar to P2.E. coliC made lysogenic for Wφ restricts the growth of λ, and elsewhere (Kerszman, Glover & Aronovitch, 1967) it has been shown that the DNA of phage λ is degraded shortly after infection of bacteria lysogenic for Wφ. A mutant of Wφ has been isolated which has lost the property of restricting the growth of λ.
Effects of X-rays on response to selection for a quantitative character ofDrosophila melanogaster
Authors: Jones L. P.
Published: September 2009

1. Lines with ten pairs of parents and selected at an intensity of 20% were exposed to 1000 r. of X-rays for 0, 2, 10 or 30 generations.

Lines which received some irradiation generally gave greater response than the unirradiated controls. The phenotypic variance in the irradiated lines was much higher than in the controls. There was little difference in behaviour between lines receiving ten generations of irradiation and those irradiated every generation. Lines receiving only two generations of irradiation had lower variances than the other irradiated lines, but in one of three replicates the response was greater than the corresponding continuously irradiated line.

3. Lethal frequencies were much higher in irradiated than unirradiated lines. Particular chromosome II and III lethals were at high frequencies in most of the irradiated lines but in only two out of five controls.

4. On relaxation, the mean of the irradiated lines generally declined considerably, but in the unirradiated lines there was only a very small regression.

5. It appears that most of the extra response and increased variance in the irradiated lines were caused by a few genes with large effect on bristle number.
Developmental genetics of leaf formation in Lolium: 1. Basic Patterns of Leaf Development in L. Multiflorum and L. Perenne
Authors: Edwards K. J. R.
Published: September 2009

1. Repeated measurements on the growth of individual leaves in seedlings and young plants of ryegrass combined with dissections of the apex of the shoot and of very young leaves have shown that the basic pattern of leaf formation is very similar in Lolium multiflorum and L. perenne.

2. The initial growth rate of a leaf primordium is low but increases suddenly at a point when the primordium is somewhat longer than the apex and about 1 mm. in length. After this transition, which I have called the unfolding of the leaf, the rate of elongation is faster and more or less linear until the leaf is nearly mature.

3. The time of unfolding of a leaf is very closely associated with the time of maturity of the next older leaf on the same side of the apex. Thus a leaf ceases growth when the next younger leaf immediately above it starts elongating rapidly, though which is cause and which is effect is it not possible to say.

4. This close relationship between duration of leaf elongation and rate of unfolding of successive leaves holds for both species in two seasons. It leads one to predict that selection for increased leaf size, in so far as it is a result of greater duration of leaf elongation, is likely to be accompanied by a slower rate of leaf appearance, and conversely that selection for rate of leaf appearance is likely to result in smaller leaves.
Developmental genetics of leaf formation in Lolium: 2. Analysis Of Selection Lines
Authors: Edwards K. J. R.
Published: September 2009

Detailed measurements of leaf growth and leaf dimensions in the seedling stage were made on lines which had been selected either for large or small leaf size or for fast or slow rates of leaf appearance within one population of Lolium multiflorum (Italian ryegrass) and two populations of L. perenne (Irish perennial and Hunsballe perennial ryegrass).

Selection for either character had no effect on the rate of initiation of primordia at the apex, but did change the rate at which successive primordia became leaves. This rate of unfolding was very highly correlated with the rate of visible appearance of leaves and in all cases showed a parallel response to selection for the latter, as did also the rate of maturation of leaves. All three rates showed a negative correlated response to selection for leaf size.

Selection for increased leaf size in all cases led to a longer duration of the elongation of an individual leaf, but selection for faster rate of leaf appearance always reduced this duration. The rate of elongation of individual leaves increased under selection for larger leaf size but showed irregular changes under selection for faster leaf appearance, going down in Irish but up in Hunsballe.

Data for dimensions of cells from the lower epidermis showed that changes in leaf length under selection were sometimes associated with changes in cell length, some-times in cell number and sometimes with both.

Selection had in no case disrupted the close association between the maturation and cessation of growth of a leaf on the one hand, and, on the other, the unfolding from the apex and onset of rapid growth of the next younger leaf on the same side of the apex. Thus in all lines only two leaves (one on each side of the apex) were elongating rapidly at any one time, and an increase in the rate of unfolding was associated with a decrease in the duration of elongation and vice versa.

This association was the basis of the observed negative correlated responses between leaf size and rate of leaf appearance. But the fact that the rate of elongation could change independently of the duration opened up the possibility of setting up a selection criterion which would increase the total rate of leaf area formation.

The value of this kind of analysis of a character complex in a plant-breeding programme is suggested to lie in discovering physiologically or developmentally limiting processes rather than merely identifying morphological components.
Behavior of three colicine factors and an R (drug-resistance) factor in Hfr crosses inSalmonella typhimurium
Authors: Dubnau Eugenie , Stocker B. A. D.
Published: September 2009

An LT2 Hfr strain,his metC gal, was crossed to a multiply marked LT2 F−line. Analysis of recombinant yields, segregation of unselected markers and interrupted matings indicated injection of the Hfr chromosome in the sequence

The introduction into the Hfr of the colicine factorscolI, colE1andcolE2and the R factorR2had little or no effect on its fertility. All four factors were transmitted at low frequency to the F−population, and to recombinants at higher frequencies (colI5–30%,colE130–80%,colE25–30%,R20–9%). Transfer ofcolE1occurred before 20 min., that ofcolE2andcolIlater than 100 min. Segregation data did not reveal close linkage of any factor to any chromosomal locus, but recombinants with a long stretch of donor chromosome were more likely than others to have acquiredcolE2andcolI. Nearly all recombinants andF−cells which acquiredcolIorcolE2acquired both, andcolE1also. Most cells which acquiredR2acquired one or more colicine factors. These plasmid associations can be formally represented by transfer of plasmids, independently of the chromosome, in the sequencecolE1—(colI, colE2)—R2. Phage P22 grown on the Hfr carrying the four plasmids transduced thetet-rtrait ofR2at very low frequency, and thesul-r str-rcharacters, together, at low frequency. Some of each sort of drug-resistance transductant, but no transductants in respect of chromosomal characters, acquiredcolEl or colE2by co-transduction.
Two-way selection for body weight in Tribolium on two levels of nutrition
Authors: Hardin R. T. , Bell A. E.
Published: September 2009

Parameters necessary for predicting direct and correlated responses for large and small 13-day larval weight in T. castaneum on two levels of nutrition were estimated in the base population. Larval weight in the GOOD environment was approximately twice that observed in POOR. Heritabilities (estimated from the ratio of sire component to total phenotype variance) of larval weight on the two rations were similar, 0·21 ± 0·06 and 0·19 ± 0·05 for GOOD and POOR, respectively. Heritabilities based on dam-offspring covariances were similar to these, but those obtained from full-sib covariances were much larger (0·97 ± 0·07 for GOOD and 0·69 ± 0·07 for POOR). This suggested that considerable dominance rather than maternal effects were present. The genetic correlation between growth on GOOD and growth on POOR was estimated as + 0·60 ± 0·21.

The selection experiment was replicated four times with each replication extending over eight generations. Good agreement between predicted and observed values for direct selection was observed for large selection in both environments and small selection in POOR. However, response to small selection in GOOD was significantly greater than predicted in all four replications and was associated with increased selection differentials. Realized heritabilities were approximately the same for both directions in GOOD yet asymmetrical responses occurred for all replications due to unequal selection differentials. On the other hand, realized heritabilities were asymmetrical in POOR. Those observed for small selection were more than twice the size of those calculated for large lines. However, the responses in POOR were symmetrical since the selection differentials varied inversely with the realized heritabilities.

Because of the asymmetry observed for heritabilities and selection differentials, correlated responses were poorly predicted. The average effective genetic correlation between growth in GOOD and growth in the POOR environment agreed remarkably well with the base estimate, yet asymmetry of the genetic correlation was a consistent phenomenon with values for the large lines being less than the base parameter while small lines were uniformly larger.

Asymmetries of the various genetic parameters were not anticipated from base estimates. They were not caused by sampling or chance fluctuations since all four replications were remarkably consistent. Asymmetry for any one genetic parameter (e.g. heritability) was associated with a particular environment or direction of selection while other genetic parameters reacted asymmetrically in populations exposed to a different set of environmental treatments.

For maximum performance in a single environment, these results show that selection should be practiced in that environment. With regard to mean performance in GOOD and POOR environments, selection for large size in POOR gave some 25% more gain than selection in GOOD. Selection for small size in either environment was equally effective in obtaining minimum size in both environments.
Gene action in the mammalian X-chromosome
Authors: Grüneberg Hans
Published: September 2009

Contrary to opinions expressed by various authors, the phenotype of heterozygotes for mammalian sex-linked genes gives no support for the Lyon hypothesis (L.H.). Evidence, mainly from the mouse, shows that in such heterozygotes, both alleles act together as in autosomal genes.

In the present paper, it is shown that neither the behaviour of double heterozygotes for sex-linked genes nor that of X-autosome translocations provides independent evidence in favour of the L.H.: in each case, the interpretation depends on that of the behaviour of single heterozygotes and hence fails to discriminate. Moreover, new facts from both types of situation are also contrary to the L.H. In particular, a unified interpretation which fits the behaviour of genes in all known types of X-autosome translocations in the mouse requires the assumption that partial inhibition of gene action happens in both X-chromosomes of mouse females, and presumably the females of other mammals. The new hypothesis is consistent with all relevant genetical facts and, like the L.H., it also accounts for dosage compensation.
Maintenance of heterozygosity at the mt locus after autogamy in Euplotes minuta (Ciliata Hypotrichida)
Authors: Nobili R. , Luporini P.
Published: September 2009

The genetic consequences of autogamy have been analysed in the autogamous strain A-25 of E. minuta. During autogamy as well as during conjugation four pronuclei (two genetically identical pairs) are formed in each individual. In conjugating pairs, any two of the four pronuclei of the autogamous conjugant may participate in synkaryon formation. Consequently, an 8:13 segregation ratio of clonal and synclonal mating-type inheritance has been found to occur in the progeny obtained by crossing A-25 animals with non-autogamous animals. During autogamy, synkaryon formation appears to be brought about by a preferential karyogamy of genetically dissimilar nuclei more often than is expected on a random basis. Therefore, heterozygosity is usually maintained after autogamy in spite of the extreme inbreeding characteristics of this sexual process.
Genetic analysis by means of the parasexual cycle inAspergillus niger
Authors: Lhoas Pol
Published: September 2009

An investigation of mitotic segregation and recombination inA. nigergave the following results:

1. Thirty-one non-allelic markers have been assigned to six linkage groups (containing 11, 9, 6, 3, 1 and 1 markers respectively) by the analysis of haploid mitotic segregants from synthesized diploids.

2. The sequence of nine markers in one linkage group was determined and some of the map intervals were estimated by the analysis of haploids, recombinants for linked markers.

3. Almost all the haploid segregants were obtained on medium supplemented with the aminoacid analogue,p-fluoro-phenylalanine, the action of which is interpreted as an induction of chromosome losses.

4. The rates of mitotic crossing-over and haploidization are much higher than in the sexual speciesA. nidulansand the data support Pontecorvo's (1958) suggestion that the parasexual cycle can be a substantial alternative to the sexual cycle.
The effects of inbreeding on the components of litter size in mice
Authors: McCarthy J. C.
Published: September 2009

Twenty-four lines were bred from a base population of outbred Q mice by continued full-sib mating. Inbreeding depression in litter size at birth was observed. This decline in litter size was analysed in terms of ovulation rate, the incidence of preimplantation mortality and the incidence of postimplantation mortality. Pregnant females were dissected at 17½ days' gestation and the numbers of corpora lutea, or eggs, and of live and dead embryos were counted. Matings were arranged so that separate estimates of the effects of inbreeding in the mother and in the litter on the components of litter size could be obtained.

In the first generation of inbreeding when the inbreeding coefficient of the litter was raised from 0 to 25% decline in litter size was attributable to an increased incidence of preimplantation mortality.

In the second and fourth generations decline in litter size was attributable to (1) a reduction in the number of eggs ovulated by the inbred mothers, (2) an increased incidence of preimplantation mortality which resulted from inbreeding in the mother. No evidence of significant effects on mortality of inbreeding in the litter was obtained in the later generation of inbreeding.

These findings are discussed in the context of previous work on the effects of inbreeding and crossing on litter size and its components in mice and pigs.
Inversion heterozygosity and selection for wing length inDrosophila subobscura
Authors: Prevosti Antonio
Published: September 2009

1. Selection for long or short wings was carried out in three pairs of lines of which two were started from the same basic population. At the end of the selection experiment the frequencies of the chromosomal arrangements were determined in each line and compared with the corresponding original frequencies to see if the chromosomal polymorphism ofDrosophila subobscurais related to the genetic variation of size in a regular way.

2. The three pairs of lines show an asymmetrical response to selection. Selection for long wings is less effective in changing the mean of the population than selection for short wings.

3. Heritability is lower in the lines selected for long wings, especially in the later generations of selection.

4. Viability shows a very small decrease during selection in most selected lines.

5. In no case does the coefficient of variability show statistically significant changes, but there is a general tendency for it to decrease.

6. Selection for long wings favours combinations heterozygous for the standard chromosome orders and specific complex inversion orders. Selection for short wings generally fixes in homozygous combination specific complex inversion orders.

7. The heterozygous combinations of the standard chromosomal orders, which are most frequent in northern populations, when combined with the complex inversion orders which are most frequent in southern populations, have a heterotic effect on size.

8. The complex inversion orders usually fixed in homozygous combinations in the lines selected for short wings are those most frequent in southern populations which have a smaller mean size than northern populations.

9. The blocks of genes integrated in ‘supergenes’ in the inverted segments of the chromosomes ofD. subobscuradiffer in genetic composition with respect to the control of wing length.
A serum esterase variation inMicrotus agrestis(L.)
Authors: Russell M. A. , Semeonoff R.
Published: September 2009

1. An investigation of the serum esterases of the field-vole,M. agrestis, has been carried out by the method of starch-gel electrophoresis.

2. A total of 254 animals, mainly from Carron Valley, near Stirling, have been examined.

3. Evidence is presented for a system of four enzymes controlled by two genetic loci, which it is proposed to call Es-3C and Es-3R.

4. Each locus specifies one polypeptide sub-unit of the E3enzyme, which is a dimer.

5. The two loci each have two alleles present at high frequencies in the population examined.
Chromosome instability related to gene suppression inAspergillus nidulans
Authors: Ball C.
Published: September 2009

A complicated system of chromosome instability related to gene suppression has been analysed. In addition, unstable genetic events analogous to those previously described inA. nidulansand in other organisms have been detected and one type of unstable variant recovered may be determined by V-type position effect. Furthermore, the selective systems used, clearly offer scope for analysis of genetic instability in general.
Heterokaryon studies of the cytoplasmic mutant SG in Neurospora
Authors: Puhalla John E. , Srb Adrian M.
Published: September 2009

Heterokaryons were made between a cytoplasmic variant of Neurospora called SG, which shows a slow growth rate, and normal strains. Fusions were made in such a way that the fate of the protoplasmic mixes in individual hyphae could be followed. A semi-quantitative analysis of nuclear and cytoplasmic migration along established hyphae was possible. Apparently, components of SG and normal cytoplasms are able to associate intimately in a single hyphal segment and later segregate intact. More often, however, an interaction of cytoplasms occurs which results in a new stable cytoplasmic type called slow SG. It is postulated the cytoplasmic determinants of SG are particulate and that the slow SG strains are the result of reassortment of the SG factor with other autonomous cytoplasmic entities. Acriflavine in the proper concentration inhibits and kills SG strains on solid medium without affecting normal strains. The acriflavine is most effective against germinating spores. The SG phenotype is redefined on the basis of this sensitivity to acriflavine.
Linkage of one component of the major urinary protein complex of mice to the brown coat color locus
Authors: Hudson D. M. , Finlayson J. S. , Potter M.
Published: September 2009

Two codominant alleles,Mup-a1andMup-a2, controlling electrophoretic variation of one of the components of the major urinary protein (MUP) complex of the mouseMus musculushave been found to be linked to the black–brown coat color alleles (linkage group VIII).
A comparative genetical study on DDT resistance in adults and larvae of the mosquitoAedes aegyptiL
Authors: Wood R. J.
Published: September 2009

Inheritance of DDT resistance has been studied in crosses between the highly resistant ‘T’ strain ofA. aegypti(constituted by inbreeding from the TRINIDAD DDT-resistant stock) and the ‘64’ susceptible strain.

Larval DDT resistance derives from a major geneRDDT1on linkage group II, the order beingRDDT1–s–y. Linkage group III may also contribute to larval resistance. Linkage group I makes no contribution.

Adult DDT resistance derives from a major geneRDDT2, 18·2 ± 2·1 units from the marketblton linkage group III. Linkage group II has no influence on adult resistance.

Selection with DDT to retain onlyRDDT1/+ segregants in larvae of backcrossesRDDT1/+×+/+ did not increase resistance in resulting adults, confirming the difference in genetic mechanism at the two stages.

The F1progenies from reciprocal crosses between ‘T’ and ‘64’ differed slightly but significantly in larval resistance, modifying the influence of the major geneRDDT1in the heterozygote.

The early developmental stages of theRDDT1/+ phenotype (up to the fourth larval stage) were more viable than the +/+ phenotype in backcross segregation. The difference in mortality probably exceeded 30%.
Cell number in relation to heterosis during embryonic growth of mice
Authors: Krzanowska H.
Published: September 2009

Body and liver weight and the number of nuclei in the liver were significantly higher in F1hybrid than in inbred embryos developing in the same uterus after artificial heterospermic insemination. The size of 13-day-old F1hybrids corresponds to the size of 13·4-day in bred embryos. No significant differences in cell size were found between F1hybrid and inbred embryos of the same age. It is concluded that in 13–15-day embryos heterosis takes place through increase in cell number and not cell size.
Effects of acriflavine on the transfer of episomes and bacterial chromosome inEscherichia coliK-12
Authors: Arai Toshihiko , Watanabe Tsutomu
Published: September 2009

The effects of acriflavine on the transfer of various episomes and of the bacterial chromosome were studied using acriflavine-sensitive and -resistant strains ofE. coliK-12 as donors and recipients. It was found that the inhibition of transfer of these elements by acriflavine was only slight when donor bacteria were resistant to this acridine dye, regardless of whether the recipient bacteria were acriflavine-sensitive or -resistant. This result seems to support the view that acriflavine inhibits the replication of these elements in donor bacteria which is considered essential for their transfer. With colicinogenic factors, in contrast to F and R, the results were affected by the sensitivity or resistance of the recipient and were in support of the killing by acriflavine of the cells which received the colicinogenic factors.
Sgene polymorphism inNicotiana
Authors: Pandey K. K.
Published: September 2009

Interspecific crosses between, different genotypes and species ofNicotianahave revealedSgene polymorphism on a large scale. In the usually yellow-flowered self-compatible speciesN. glaucaa strain occurs that has a self-incompatibility gene which is tightly linked with the bright-red corolla colour gene. In self-incompatible species, there are two kinds of self-incompatibility alleles,SIandSFI, distinguished on the basis of the acceptability ofN. langsdorffiipollen. TheSIform has a large number of alleles whereas theSFIform has only two,SF10andSF11. TheSIalleles are again divisible into two groups on the basis of the acceptability ofN. noctiflorapollen and, on the same criterion, the twoSFIalleles,SF10andSF11, also are distinguishable.N. noctifloraandN. bonariensisplants could be divided into two and three groups respectively on the basis of interspecific compatibility relationships. When plants of each species were crossed among themselves, they formed two and three intra-incompatible and inter-compatible groups respectively, identical with those found on the basis of interspecific compatibility relationships. The significance of this observation is at present not fully understood.
Aromatic amino acid biosynthesis and para-fluorophenylalanine resistance inAspergillus nidulans
Authors: Sinha Umakant
Published: September 2009

1. Five additional phenylalanine (PHE)-requiring mutants have been isolated but they do not add to the number of loci already known which have been designatedphenA(phen2and its alleles) andphenB(phen6).

2. Two pathways for tyrosine (TYR) synthesis inA. nidulanshave been proposed: the well-known one by the transamination ofp-hydroxyphenylpyruvic acid and an alternative one, as in animals, by the hydroxylation of PHE.

3. Ten allelic partial TYR-requiring mutants (tyrA), presumably blocked in the transamination pathway, have been isolated after N-methyl-N′-nitro-N-nitrosoguanidine (NTG) treatment ofbil;phenA3 conidia.

4. Four partial TYR requirers (at another locus—tyrB) have been isolated after NTG treatment oftyr A7, bi1conidia. They are presumably blocked in an alternative pathway for TYR synthesis, i.e. in the PHE-hydroxylation pathway.

5.tyrAmutants have been found to bep-fluorophenylalanine (FPA)-resistant and allelic to mutants at thefpAlocus.tyrBmutants have been found to be very leaky and FPA-sensitive.tyrA;tyrBdouble mutants have been found to be exacting TYR requirers.

6. Mutants at locifpA(tyrA) andfpE(anthranilic acid-requiring) have been interpreted to bep-fluorophenylalanine-resistant due to an oversynthesis of PHE.
Unbiased second-division segregation inNeurospora
Authors: Srb Adrian M. , Jarolmen Howard
Published: September 2009

Results of crosses of a large number of Neurosporas of different origin, including several distinct strains ofN. sitophila, were utilized to re-examine the question of whether certain wild-type Neurosporas other thanN. crassashow biases in the two types of second-division segregation. Segregations for alleles of the mating type andpeakloci on a wide variety of genetic backgrounds gave little evidence for excess either of symmetrical or asymmetrical ‘post-reduction’ asci.
Genetic divergence in M. Vetukhiv's experimental populations ofDrosophila pseudoobscura: IV. Relative viability
Authors: Kitagawa Osamu
Published: September 2009

Six experimental populations ofD. pseudoobscurawere maintained at three different temperatures for more than 8 years. All the populations have originally descended from the same founders. The populations were examined for evidences of genetic divergence. The pre-adult viabilities of the flies from these populations, and of their F1and F2hybrids, were studied at 16°C., 25°C., and 27°C. The results indicate that the populations have diverged genetically from each other. Some divergence is observed not only between populations kept at different temperatures, but also between the replicate populations kept at the same temperature.
Genetic control of maturity inTetrahymena pyriformis
Authors: Bleyman Lea K. , Simon Ellen M.
Published: September 2009

A new mutation,Em, is described forT. pyriformis, syngen 1. This dominant mutation eliminates the normal immature period in heterozygotes but is lethal in the homozygous state.

This paper is dedicated to Dr. Ralph Cleland in honor of his 75th birthday.
Further studies on inherited susceptibility to Friend mouse leukemia virus
Authors: Franker Colin K. , Quilligan J. J.
Published: September 2009

Analysis of F1BC1 and BC2 progeny from matings of inbred DBA/2 and C57BL mice confirm the existence of a single major gene for C 57 BL-resistance to Friend virus. The doses of virus used did not obscure expression of this Mendelian unit.
Calcium and phosphorus metabolism in the grey-lethal mouse
Authors: Murphy Helen M.
Published: September 2009

Ca and P metabolism in the grey-lethal mutant mouse has been investigated. This animal is hypocalcaemic and hypophosphataemic and the serum alkaline phosphatase is elevated far above the normal. Increased bone ash content has been attributed to an elevated bone Ca. Fromin vitroexperiments involving steady-state distributions of calcium and phosphate it is concluded that active bone metabolism is reduced in mutant bone. This reduced ratio may be attributed to an increased passive ion solubility.

These results tend to the assumption of an hormonal imbalance in this mutant system. An increased production of thyrocalcitonin has been postulated to account for these findings.
The effects of inbreeding on birth weight and foetal and placental growth in mice
Authors: McCarthy J. C.
Published: September 2009

Twenty-four lines were bred from a base population of outbred Q mice by continued full-sib mating. Inbreeding did not cause depression in mean birth weight. However, convincing evidence of inbreeding depression in foetal weight at 17½ days' gestation was found; this depression in the rate of prenatal growth was attributable both to inbreeding in the litter and the mother. It was also inferred from the results of crossing the partially inbred lines that inbreeding in the litter caused depression of placental weight. It is concluded that the genes controlling the rate of prenatal growth exhibit directional dominance but that the resulting inbreeding depression in this trait does not lead to a lower birth weight, possibly because of the compensating effect of a longer period of gestation.
The effect of repeated cycles of selection and regeneration in populations of finite size
Authors: Curnow R. N. , Baker L. H.
Published: September 2009

Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population are used to develop an iterative method for studying the effects of repeated cycles of selection and random mating. This is done by assuming a particular, but flexible and probably realistic, approximate form for the distribution of gene frequencies at each generation.

The method gives for each generation the first two moments of the gene frequency distribution, the expected gain from selection, the probabilities of fixation and also the variability of gain. The variability of gain is of considerable importance in evolution, selection experiments and in plant and animal breeding programmes.

Kojima's (1961) formulae have been extended to allow for differentiation between males and females. Hence different selection intensities and population sizes for the two sexes can be studied. Selfing with selection is considered separately. Extensions to cover simple examples of multiple alleles, linkage and epistasis are possible. Reference is made to previous work using transition matrices.
Interspecific reciprocal hybrids between Mesocricetus auratus and M. newtoni
Authors: Raicu P. , Bratosin S.
Published: September 2009

Our previous research (Raicu & Bratosin, 1966; Raicu, Hamar, Bratosin & Borsan, 1967) has shown that the Romanian hamster (Mesocricetus newtoni, 2n 38) is a well-established species, differing considerably from the Syrian hamster and from other hamster species. The species is spreading in the south of Romama, especially in Dobrudja, and in Bulgaria. Its spreading area is completely isolated from the spreading area of all other species of Mesocricetus. The preferred biotops are uncultivated fields, dry steppes and fields cultivated with fodder plants. The Romanian hamster reveals important differences in the number and structure of the autosomes and in the degree of homology and presence of chiasmata in the heterosomes.
Variation of scutellar bristles inDrosophila: XI. Selection for scutellar microchaetae and the correlated response of scutellar bristles
Authors: Scowcroft W. R.
Published: September 2009

The third chromosome mutant,hairy1, adds a varying number of microchaetae to the scutellum. The genetic relationship between this character and scutellar bristles was investigated using the conventional techniques of full- and half-sib analysis of variance and covariance, direct and correlated response to selection for microchaetae and scutellars respectively and diallel crosses at two stages in the programme. There was a good correspondence between the predicted and realized divergence resulting from selection for increased and decreased microchaetae. The correlated response in scutellar bristles appears to be accounted for primarily by genetic changes in microchaetae.
Polymorphism of plasma esterases in flounder and plaice
Authors: de Ligny Wilhelmina
Published: September 2009

Esterase activity was detected in starch-gel electropherograms of plasma samples from two species of teleost: flounder and plaice. In both species polymorphism was found. In flounder its genetic origin was indicated by population genetical data. Differences in staining intensity of the individual bands were found to be correlated with length of the animals.
Loci of radiation sensitivity in Bs strains of Escherichia coli
Authors: Donch John , Greenberg Joseph
Published: September 2009

The genes responsible for u.v. sensitivity in ten sensitive mutants ofE. colistrain B (Bs strains of R. Hill) have been mapped by transduction. Theuvrgenes of all the mutants able to reactivate u.v.-irradiated phage (HCR+), including Bs2, 4, 5, 6, 7, 9 and 10, were linked, 50–95%, withmalB. The gene of Bs12 (HCR) was also linked tomalBas isuvr A. The gene of Bs8 (HCR) was linked togal, that of Bs3 (HCR) tohis. Transduction ofmal+from a strain withuvr A, or amal+derivative of Bs12, to Bs2, 4, 5, 6, 7, 9 or 10, yielded about 30% u.v.-resistant transductants. Amal+transduction with Bs2mal+as donor and other Bs strains as recipients yielded < 0·1% u.v.-resistant transductants. ThemalB-linkeduvrgenes of all mutants (except Bs3 and Bs8) were transducible withmetA. The quasi-reciprocal crosses and three-point tests suggested the order of markers asmetA malB uvr(HCR+)uvr(HCR). The sensitivity gene of Bs9 was exceptional in that it appeared to lie betweenmetAandmalB. The sensitivity gene of Bs11 could not be mapped because transductants to that strain were not possible, nor did it act as a recipient in sexual recombinations.
The positions of the centromeres in linkage groups II and IX of the mouse
Authors: Lyon Mary F. , Butler Jane M. , Kemp Richard
Published: September 2009

In mice heterozygous for translocation T(2;?)163H, and also for linkage group II markers, thecwlocus shows close linkage with the point of rearrangement (about 1−2% recombination). Since T 163 was apparently formed by fusion of two chromosomes near their centromeres, this means that the centromere must lie at thecwend of linkage group II. In homozygotes for T(2; 9)138Ca the genesTanddshow significant linkage, indicating that their loci are on opposite sides of the trans-location break. Since, from previous data, the break is known to be proximal tod, it must then be distal toTand, again from previous data, the order of loci hi linkage group IX must be centromere-T-tf-T 138 break.
Mating-type alleles in Illinois strains ofTetrahymena pyriformis, syngen 1
Authors: Phillips Ruth Brosi
Published: September 2009

Two new wild strains ofT. pyriformis, syngen 1, have been examined for new matingtype, serotype and isoenzyme alleles. No new alleles at the mating type (mt) locus were found, but the two alleles previously found were extracted. No new alleles were found at the other five loci examined, but two alleles were obtained for each locus. These observations indicate that a limited polymorphism exists for these loci in natural populations ofT. pyriformis, syngen 1.