Results Of Breeding Experiments Research Articles

Chara globata Mig. (Streptophyta: Charales): rare species revised

A rare species Chara globata Mig. has a distinct habit and may be referred to as a flagship species. Here we describe a wide range of vegetative and reproductive morphologies in C. globata in localities distant from the locus classicus. In contrast to the known holotype features, the specimens studied consistently displayed a generally tylacanthous diplostichous stem cortex which is in agreement with protologue. Based on morphology, phylogenetic affinity (this study) and results of breeding experiments (Proctor 1971, 1975), we proposed that C. globata should be transferred to the section Chara. Current data suggest that C. globata is a species with a disjunctive distribution, mainly in the arid and semiarid regions of Eurasia. Specimens collected from the end of the 1960s to the beginning of the 1970s confirmed the existence C. globata in Western Asia. The species was also recorded in Europe and the Sahara-Arabian Desert for the first time.

Adaptive differences in the timing of egg laying between different populations of birds result from variation in photoresponsiveness

Although intraspecific variation in reproductive photoresponsiveness has been demonstrated in many bird species, it has never been examined in conjunction with comparative long-term field studies which accurately identified key factors governing local adaptation of life history traits, and rarely in combination with studies of non-domesticated birds that breed in captivity. Furthermore, it is generally assumed that, within species, adaptive differences in photoresponsiveness mainly occur across populations breeding at different latitudes, and that at similar latitudes, interpopulation variations in timing of breeding is mainly caused by proximate responses to variations in micro-climate or food. Considering results of breeding experiments in laboratory conditions in the framework of long-term comparative studies of natural populations, we here provide the first evidence in a bird that adaptive differences in the onset of first clutches between populations breeding at similar latitudes proximately mainly results from variation in responses to daylength.

A new black tarsomere allele in Aedes aegypti (Diptera: Culicidae) from the island of Grand Comoros.

We report the results of breeding experiments between the new mutant and normal A. aegypti and a strain homozygous for black tarsomere (blt)

XX sex reversal in the American cocker spaniel dog: phenotypic expression and inheritance.

This study was conducted to define the range of phenotypic expression and mode of inheritance of XX sex reversal in the cocker spaniel dog. Breeding experiments produced F1, F1BC, and F2 generations in which 29 XX true hermaphrodites and 3 XX males were defined by chromosome constitution, serial histologic sections of the gonads, and examination of the internal and external genitalia. In XX true hermaphrodites, the most common combination of gonads was bilateral ovotestes, followed by ovotestis and ovary, then ovotestis and testis. The amount of testicular tissue in the two gonads was closely correlated within each true hermaphrodite. The distribution of testicular tissue within ovotestes of true hermaphrodites was consistent with the hypothesis that testicular differentiation is initiated in the center of the gonad and spreads outward. XX males had bilateral aspermatogenic testes and the internal ducts and external genitalia were more masculinized than in true hermaphrodites. Results of breeding experiments are consistent with autosomal recessive inheritance, the affected phenotype being expressed only in dogs with an XX chromosome constitution. The phenotypic expression and mode of inheritance of this disorder is compared to XX sex reversal in humans and other animals.

Effects of nutrition on brood production and slavery in ants (Hymenoptera, Formicidae)

An artificial diet (Bhatkar andWhitcomb, 1970) was recommended for maintaining ant colonies. Comparative studies with a slave-making ant,Harpagoxenus sublaevis, and one of its slave species,Leptothorax acervorum, have shown that this diet is not sufficient for normal brood production in the independent speciesL. acervorum. In colonies of the slavemaker species fed with the diet, much more of the slave species pupae captured during raids are consumed than in colonies supplied with a more natural diet of insect tissue and honey. These experiments demonstrate that diet can seriously influence the results of breeding experiments, and we suggest that diet may be very important for certain behavioral studies as well. We conclude that the B.—W.—diet is probably inappropriate for many ant species which utilize both insect prey and honeydew.

Thomas Hunt Morgan: Materialism and experimentalism in the development of modern genetics

TIG -- May 1985 One of the most import- ant events in the develop- ment of genetics was the first application of Men- del's laws to the cyto- logical facts of chromo- some structure and be- havior. This synthesis was achieved by Thomas Hunt Morgan (1866- 1945) and a group of young enthusiastic co- workers, Alfred Henry Sturtevant (1891-1970), Herman Joseph Muller (1890-1967) and Calvin Blackman Bridges (1889-1938), working with Drosophila melanogasterat Columbia University between 1910 and 1928. By cor- relating results of breeding experiments with cyto- logical observations on chromosome structure they demonstrated that Mendel's hypothetical 'factors' could be treated as specific points, or loci, along the length of the chromosomes. These findings, with many extensions and elaborations, were summarized in the historic book The Mechanism of Mendelian Heredity ~ published in 1915 and revised in 1923. For the next several decades, Morgan and his group mapped the chromosomes of D. melanogaster and related species, providing the first comprehensive genetic map for any organism of what they called the 'architecture of the germ plasm'. For his work in eluci- dating what later became known as the chromosome theory of heredity, Morgan was awarded the Nobel Prize for Physiology and Medicine in 1933. Three-quarters of a century has now passed since Morgan published his first paper on inheritance of eye color in Drosophila in 1910 - a period that has seen genetics come to occupy the same central position in biology today that Darwinian theory occupied in the general study of natural history a century ago. It may be useful here to examine how twentieth century genetics began and how some of its underlying philo- sophical assumptions helped its rapid development, while also placing restrictions on the kinds of questions geneticists asked and the answers they con- sidered acceptable. For the last 30 years of the nineteenth century and the first ten years of the twentieth century, the study of heredity, using plant and animal hybridization, pro- ceeded independently of the cytological study of the cell nucleus and the chromosomes. Although cyto- logists were aware that the nucleus in general, and the chromosomes in particular, might well have some- thing to do with transmission of inherited traits, few studies in cytology itself threw any direct light on the issue. Similarly, students of animal and plant breeding were content to postulate the existence of hereditary particles transmitted from generation to generation, but produced no direct evidence for the nature or material composition of these units. The founder of modern genetics, Gregor Mendel (1822-1844), knew nothing of contemporary cytological work, and made no reference to chromosomes or other cell com- ponents in his original studies (1865) on hybridization *Part 2 of this article will appear in next month's TIG.

Inherited renal cysts in pigs: results of breeding experiments.

A landrace boar with a previous history of siring progeny with cystic kidneys was bred to five unrelated large white sows. Thirty-eight of 61 progeny (62 per cent) were affected with renal cysts. This incidence does not differ significantly from that expected with autosomal dominant inheritance. Three of the dams and the boar were found at post mortem examination to have renal cysts. The number of cysts may be determined by polygenic inheritance. Study of the pathology of the cysts in one-day-old, 25- to 32-day-old and 370-day-old progeny indicated a complex pathogenesis including probable recruitment to the cyst population throughout the period studied. The syndrome studied did not resemble previously described polycystic syndromes of the pig nor was it closely comparable to any of the well described polycystic syndromes and renal cystic disorders of man.

Possible duplication of the hemoglobin α chain locus in sheep

Only one type of α chain has been described so far in the hemoglobins of adult domestic sheep. A variant (Hb D) of the α chain, characterized by a substitution glycine → aspartic acid at position 15, has been described in Yugoslavian sheep. In this paper we report the identification of a second α chain (α2), observed in several sheep when the globin was analyzed by CM-cellulose chromatography or the total hemolysate submitted to isoelectric focusing. The ratio of this chain to the usual one (α1) in the globin of different animals is equal to either 1 : 2 or 1 : 4. The structural difference between α1 and α2 chains consists in the replacement of a leucine residue by an histidine in the position 113 or 114 of the polypeptide chain. Preliminary data on the frequency of the α2 chain in eight domestic breeds indicate that this chain is fairly common, being present in 15 out of 40 animals examined. The results of breeding experiments between sheep of an appropriate α chain phenotype suggest the possibility of a duplication of the hemoglobin α locus in the Ovinae.

The genetics and pathology of discrete subaortic stenosis in the Newfoundland dog

Breeding experiments confirm that discrete subaortic stenosis (SAS) in Newfoundland dogs is a specific inherited trait. Specificity of the morphogenetic abnormality is not complete, however, since matings between Newfoundlands with SAS occasionally produced pups with valvular and subvalvular pulmonic stenosis as well as SAS. The spectrum of severity of SAS ranged from a subclinical forme fruste to a severe form causing death before maturity. Well-developed subvalvular stenotic rings consisted of a base of loosely arranged fibrous connective tissue and a subendocardial region of cartilagenous tissue. Severely affected dogs, some of which died suddenly, had foci of necrosis and fibrosis in the left ventricular myocardium, associated with thickening of the intramural coronary arteries. The lesions of SAS were not found in dogs before 3 weeks of age, and the mildest form was seen only in dogs between 3 and 12 weeks of age, suggesting that SAS is not a true congenital defect but develops postnatally. It is hypothesized that the fibrocartilagenous ring of SAS is derived from persistent embryonal endocardial tissue which retains its proliferative capacity and has chondrogenic potential for some time after birth. The results of breeding experiments were not consistent with any simple genetic hypothesis, and indicate that SAS is inherited as a polygenic trait or as an autosomal dominant trait with modifiers.

Shell polymorphism in the snail Cochlicella acuta (Müller) and some data on its genetics

The principal shell variation in the snail Cochlicella acuta is described in terms of banding, extra-band opacity and ground colour. A nomenclature like that used for Cepaea is adopted for the banding and a simple descriptive one, using the terms continuously opaque and discontinuously opaque, for extra-band opacity. Ground colour is either lacking, a condition which produces shells of white appearance, or present which makes them amber coloured. The results of breeding experiments are reported, which show that much of the shell polymorphism is controlled by genes located at closely linked loci. The shell polymorphism in Cochlicella acuta is compared with that in Cepaea. Possible factors determining supergene frequencies in Cochlicella acuta are discussed. Visually selective predation by rooks, Corvus frugilegus is suggested as the influence responsible for the evolution of morphs that are cryptic in certain environments. Direct evidence of such evolutionary change is reported from sub-fossil material collected from successive strata below the present surface of fixed dunes at a site in Cornwall.

A Genetic Polymorphism of Peromyscus 7Sγ1 Globulins: Detection by Differences in Electrophoretic Mobility

Abstract A genetic polymorphism for electrophoretic variants of the 7Sγ1 globulin in the deer mouse, Peromyscus maniculatus artemisiae, was demonstrated. The electrophoretic mobility of the 7Sγ1 globulin (or its Fc piece) in an individual serum represented one of three phenotypes—a relatively homogeneous fast or slow migration or a heterogeneous fast-slow mobility. All three phenotypes were detected in male and female mice from laboratory-reared and wild populations. Results of breeding experiments indicated that the electrophoretic variants were the result of two codominant alleles of the 7Sγ1 H chain gene. The unusual expression of 7Sγ1 allotype by electrophoretic variants in both Peromyscus and Mus musculus suggests that this mutational event occurred in a common ancestor.

THE MANIFOLD EFFECTS OF GENES AFFECTING FRUIT SIZE AND VEGETATIVE GROWTH IN THE RASPBERRY

SummaryA mutation found in the raspberry variety Mailing Jewel had bigger fruiting laterals, flowers and fruits than the parent stock. The results of breeding experiments were consistent with the hypothesis that the change was caused by mutation of a single gene from the homozygous to the heterozygous state, and that the gene concerned has functions whose effects are seen at each stage of development. These effects were to depress slightly the amount of vegetative, or first year's, growth and to increase the amount of reproductive, or second year's, growth. It is suggested that genes of similar function may account for differences which distinguish the raspberry from certain related species. The mutant gene is useful for plant breeding purposes. Its possible effects on the physiology of the plant are also discussed.

Evidence for the discontinuity of plastids in the sexual reproduction of a plant

Investigation of the fine structure of the egg cell of Pteridium aquilinum , a fern, reveals that the mature egg contains only large amoeboid proplastids, strikingly different from the plastids of the central cell. Early in the life of the egg there is a phase in which numerous vesicular bodies, less than 1 μ in diameter and identified as degenerate plastids, are present in the cytoplasm. As the egg matures these bodies gradually disappear, and simultaneously the nucleus of the egg throws out conspicuous evaginations. Many of these, particularly toward the end of the maturation process, and for about 6 hours after fertilization, are saclike, the contents being in continuity with the nucleoplasm. Arguments are presented for believing that these saclike evaginations become detached, and form plastid initials. Their subsequent development is similar to that of the plastid initials of embryonic cells, and the proplastids so formed replace those eliminated early in the maturation of the egg. This interpretation is held to be compatible with the results of breeding experiments with variegated plants.

SEX-LINKED ALBINISM IN THE JAPANESE QUAIL.

From a single white Coturnix chick hatched in August 1963, a white colony has been developed. The results of breeding experiments are consistent with the view that the albinism is sex-linked and recessive. It appears likely that the mutation occurred in the first white female hatched, or her sire.

Sex-Linked Albinism in the Japanese Quail

From a single white Coturnix chick hatched in August 1963, a white colony has been developed. The results of breeding experiments are consistent with the view that the albinism is sex-linked and recessive. It appears likely that the mutation occurred in the first white female hatched, or her sire.

Some breeding experiments withcepaea nemoralis (L.)

1. Preliminary results of breeding experiments are in agreement with the findings of previous workers that pink is dominant to yellow, the absence of bands is dominant to the presence of bands, and the loci controlling pink and the absence of bands are linked. 2. There is at least one major gene affecting the shade of pink; in most of the broods observed there appears to be a locus separate from the locus controlling colour, with pale dominant to medium. In one, however, it appears more likely that pale and medium pink are closely linked to, or allelomorphs at, the locus controlling colour, with pale pink not dominant. 3. Brown is dominant to the absence of brown, whether this be pink or yellow, and is linked to the locus controlling the absence of bands; if not an allelomorph of the locus controlling pink to yellow, it is at least very closely linked to it. 4. The banding pattern 00300 is due not to an allelomorph of 00000, but to the action of a modifier on 12345.

Studies onStreptocarpus

An account is given of the flower colours, chromosome numbers and flower pigments of cultivated species and hybrids ofStreptocarpus. The origin of the garden strain is recounted and the results of breeding experiments within the strain are shown to agree with the known origin of the garden forms. The action of the flower colour genes is as follows.A is necessary for the production of anthocyanin, and alone, produces anthocyanins derived from pelargonidin.R in the presence ofA produces anthocyanins derived from cyanidin.O, is epistatic toR and in the presence ofA gives anthocyanins derived from delphinidin. ThusR adds one substituent hydroxyl (or methoxyl) group to the anthocyanidin molecule andO adds two.D produces 3 : 5-dimonoside in place of pentoseglycoside-dimonoside (d) mixtures. Seven distinct colour classes results from the combination of these genes. Methylation is complete with the delphinidin derivatives but incomplete with the cyanidin derivatives.

IV.—The results of breeding experiments on the genus Leptocyclops G. O. Sars, with some general notes on the results of culture experiments

1. 1. Leptocyclops agilis Koch and L. speratus Lilljeborg are two separate species, and so are L. macruroides Lilljeborg and L. lillieborgi Sars. 2. 2. Cyclops agiloides Sars is not a separate spec...

THE EASTERN NORTH AMERICAN SPECIES OF THE GENUS EPHEMERELLA AND THEIR NYMPHS (EPHEMEROPTERA)

In a recent paper (1931, Can. Ent., LXIII, 30 et seq.) I reviewed the bicolor group of the genus Ephemerella and in the present one I purpose dealing with the remainder of our eastern species and tabulating the results of breeding experiments, carried on during the past three years by Messrs. Walley, Milne and myself, as far as they relate to this genus.

Biological Studies of Aphis rumicis, Linn.

This is the first of a series of papers based on results of breeding experiments and on observations in the field. It is hoped that a full inventigation of the biology of this species will be of value in elucidating the many difficult biological problems of the Aphididae.