Showing papers in "Genetics in 1938"

The Production of Homozygous Deficient Tissues with Mutant Characteristics by Means of the Aberrant Mitotic Behavior of Ring-Shaped Chromosomes.

Abstract: This lengthy article stemmed from McClintock's discovery of ring chromosomes in 1932 and research she conducted on the gene bm1, or brown midrib, after returning to the University of Missouri in 1938. McClintock concluded that the extent of variegation in a mature plant was proportional to the size of the ring that was sometimes lost at cell division.

X-Ray Induced Chromosomal Alterations in Drosophila Melanogaster.

Abstract: N THE fall of 1936 the first two authors began a series of experiments I to determine the frequency of minute inversions in material treated by X-rays. Before long it was realized that the frequency of such inversions is very low and that a reliable analysis would involve such technical difficulties that it would require a great deal more time than was available to the authors. Therefore, the original plan was revised and a new experiment started to determine the relation between X-ray dosage and the frequency of chromosomal breaks, the distribution of breaks along the chromosomes, and related problems. Subsequently when the experimental part of the problem was well under way the third author joined in the work. The first author is responsible for the cytological analysis of the major portion of the female material, the second author was in charge of breeding and X-raying work and helped with the cytological analysis, and the third author is responsible for the cytological analysis of all male material and of a portion of the female data where Swedish-b females were mated with treated Oregon-R males. Permanent preparations of 1765 pairs of salivary glands were used for this study. Slides were prepared by Mr. HERSCHEL ROMAN, Miss RUTH BATE, and Miss EUNICE WHITE, to whom the authors wish to express their appreciation. When this manuscript was ready for press a paper by CATCHESIDE (1938) appeared describing some of his results obtained in experiments identical with ours. Many conclusions reached by CATCHESIDE are identical with our conclusions.

The Genetics of Self-Incompatibility in Oenothera Organensis.

Abstract: ENOTHERA organensis is endemic to the Organ Mountains of 0 southern New Mexico where the entire population apparently consists of considerably less than one thousand individuak2 The morphology of the seeds indicates a relationship to members of the subgenus Oenothera (sometimes called Onagra), but the growth habit and ovule placentation resemble types belonging to the subgenus Raimannia (the Euoenothera of Engler and Prantl). Oenothera organensis has proved completely cross-sterile with five species of Raimannia. Hybrids with Oenothera species are obtained infrequently, and are almost completely sterile, resembling Oenothera-Raimannia hybrids. Oenothera organensis differs from both these subgenera in being completely self-sterile. The inheritance of self-incompatibilty in Oe. organensis proved to be of the Nicotiana type, governed by a series of multiple allelomorphs. Interest attaches not so much to the mode of inheritance as to the methods by which genetic analyses can be followed in this material.

The Development of Two Tailless Mutants in the House Mouse.

Abstract: HE events that take place in the development of the mammalian T embryo have not been subjected to an extensive causal analysis so far. The reasons for this are“to be found mainly in the lack of suitable methods. It is not possible yet to use transplantation, isolation or vital staining techniques on mammalian embryos as they have been used on amphibian embryos. In the course of time it probably will be possible to analyze the mammalian embryo by transplantation and isolation just as thoroughly as has been done with the amphibian. For the present, however, the experimenter is not able “to take an active part in the course o i events that take place during the embryogeny of the mammalian embryo,” nor “to alter the course of events a t a chosen point in a chosen manner and draw conclusions on their relations from the resulting changes.” (SPEMANN 1936.) A mutation that causes a certain malformation as the result of a developmental disturbance carries out an “experiment” in the embryo by interfering with the normal development a t a certain point. By studying the details of the disturbed development it may be possible to learn something about the results of the “experiment” carried out by the gene. However to discover anything about the nature of the action of the gene is a much harder task. It is necessary for this purpose to be able to trace back all the results of the action to certain original causes. While the experimental embryologist carries out a certain experiment and then studies its results, the developmental geneticist first has to study the course of the development (that is, the results of the developmental disturbance) and can then sometimes draw conclusions on the nature of the ‘fexperiment” carried out by the gene. In amphibian embryology the experimental analysis has led to an understanding of the causal relations of the normal developmental events. It is possible that the study of hereditary developmental disturbances and their causes in the mammalian embryo may contribute to knowledge of the causal morphology of mammalian embryology. This paper restricts itself to the description of the development of an ’ This research was aided by a grant from the Josiah Macy Jr. Foundation.

Genetics of Natural Populations. I. Chromosome Variation in Populations of Drosophila Pseudoobscura Inhabiting Isolated Mountain Ranges.

Abstract: N RECENT years there appears to be a growing interest in the I genetics of free-living populations, a subject hitherto almost untouched. Certain species of Drosophila prove to be very suitable for investigations in this field. TSCHETWERIKOFF (CHETVERIKOV), DUBININ and their collaborators in Russia, TIMOFEEFF-RESSOVSKY in Germany, GORDON in England, and STURTEVANT in this country have secured much valuable information which opens new vistas and raises a host of new problems (for a short review of the literature see DOBZHANSKY 1937). It has seemed to us that a comparison of the genetic constitutions of several free-living popu' lations from the same general region, and yet isolated from each other, may be of interest. Samples of the populations of Drosophila pseudoobscura inhabiting island-like mountain forests in the Death Valley region of California and Nevada were collected. This region is especially favorable for our purposes, since it is as yet practically undisturbed by man's activities. We wish to acknowledge our obligations to Professor A. H. STURTEVANT for his valuable advice, to Mr. H. D. CURRY whose help enabled us to collect material in certain rather inaccessible localities, and to Messrs. G. T. RUDKIN and EDWARD HELD for their assistance in conducting the experiments.

Cytogenetic Studies in Paeonia I. the Compatibility of the Species and the Appearance of the Hybrids.

Abstract: INCE 1916, the senior author has carried on an extensive series of S crossing experiments in the genus Paeonia, with the object both of obtaining new horticultural forms and of securing evidence concerning the interrelationships of the species and the processes of evolution within the genus. Some accounts of the hybrids have already been published (SAUNDERS 1928, 1933a, 193313). The junior author began cytological work on the species and hybrids in 1932, continuing that started by the late Dr. G. C. HICKS, whose work along with additional data obtained by the junior author has also been published (HICKS and STEBBINS 1934). Since that time the cytological as well as the morphological study of the hybrids has progressed steadily, except that it was somewhat interrupted by the departure of the junior author for California in 1935. The following limitations prevent a cytogenetic study of this genus comparable to that carried on in other genera, such as Crepis, Nicotiana, and Datura. Peony seeds are slow of germination, and the plant takes several years to mature; from the date of hybridization to the season of first blooms is usually a gap of six or seven years. This makes it difficult for one individual to raise many successive generations. An added difficulty is that most interspecific hybrids in Paeonia are completely sterile for a t least two or three years after they first begin to bloom; older plants of almost all the hybrids, when they have established themselves as strong clumps, set occasional seeds, usually not more than one or two to an entire plant. The size of the plants and the cost of their care through so long a period of years also make large scale experimentation for statistical data impracticable. There are in this collection a t present several thousand hybrid plants of blooming age, representing more than thirty distinct strains. The range of attempted crossings was much wider, but as was to be expected many of them persistently failed to produce seed.

Genetic and Endocrine Studies on a Transplantable Carcinoma of the Ovary.

Abstract: CARCINOMA of the ovary has been maintained by successive A transplantations in mice of the CBA strain for nearly three years. In the first study with this tumor, it was determined that only normal males of the CBA strain would show progressively growing tumors during a three-month period. It was also ascertained that the growing transplanted tumor secreted appreciable amounts of estrogen. The criteria of hormone secretion of the transplanted tumors were: (a) long continued estrous vaginal smears which, after removal of the tumors reverted to the diestrous type in castrate females; and (b) growth of the rudimentary mammary glands of males as the transplanted tumors grew. Insufficient hormone was secreted to affect the pelves (STRONG, GARDNER and HILL

The relation between satellite size and nucleolus size in three races of solanum lycopersicum

Abstract: THORT A chromosomes are associated with the nucleolus in most s wild and cultivated tomatoes but cultivated races with long A chromosomes occur commonly. A third and new type of A chromosome, much longer than the long A, was found in the summer of 1937. It is called very long A.” Both the long A and the very long A chromosomes have increased in size by large additions to the satellite end. That the increase is chiefly due to increased satellite size can best be seen in young microspores in the resting condition. At this stage the satellite remains thick and deeply stained while the rest of the chromosome is slender and pale. The same contrast between the satellite and the rest of the chromosome is evident in somatic divisions, but in meiosis the satellite can only be distinguished from the rest of the A chromosome by the position of the attachment constriction which is at or near the base of the satellite in all three types of A chromosome. Except for satellite size, long A and short A races cannot be distinguished somatically. The chromosome size of each parent is maintained in F1 and Mendelian segregation has been shown to occur (LESLEY and LESLEY 1935). The earlier literature on change in satellite size is discussed in the paper just referred to. DOBZHANSKY (1935) found that in Drosophila pseudoobscura the absolute and relative lengths of the two limbs of the Y chromosome vary, giving rise to six cytologically recognizable types of Y and that : “The morphological and physiological properties of a given strain are apparently not affected by the type of Y chromosome present in that strain.” DOBZHANSKY and BOCHE (1933) suggest that the other types of Y chromosome may have been derived from the longest V-shaped type by loss of a part of a limb. In tomato the reverse is true. Both the Y chromosome in D. pseudoobscura and the A chromosome in tomato are associated with the nucleolus and the change in size is due to changes in amount of genetically inert material. I 1

The Relation of the First Chromosome Pair to Date of Fruit Ripening in the Tomato (Lycopersicum Esculentum).

Abstract: HE linear order of four genes in chromosome I of the tomato has T been well established, principally from data obtained by LINDSTROM (1932) and MCARTHUR (1934). LESLEY (1931) has shown one of the genes in this linkage group to be related to resistance to the curly top virus disease, and LINDSTROM (1932) has demonstrated a decided relationship between fruit size and the genes in this pair of chromosomes. YEAGER (1937) has data that demonstrate the presence of a fifth gene in the group and considers this to be a major gene for fruit shape and size. The four genes that have been located by linkage tests and their arrangement are as follows : d dwarf plant recessive to D, standard plant p pubescence on the fruit recessive to P, smooth fruit o pear shape fruit recessive to 0, round fruit s compound inflorescence recessive to S, simple inflorescence

New Mutants in Sciara and Their Genetic Behavior.

Abstract: GENETIC BEHAVIOR H. V. CROUSE AND HELEN SMITH-STOCKING Department of Embryology, Carnegie Institution of Washington, Baltimore, Maryland Received January 31, 1938 H E present paper deals with six new mutant characters in Sciara T found in this laboratory. In addition, two mutants are recorded which appear to be identical with or allelic to two of these characters. Of the six, one is an autosomal dominant in Sciara coprophila Lintner, and one a sex-linked recessive in Sciara ocellaris Comstock. The remaining four, including one autosomal dominant, two sex-linked dominants, and one sex-linked recessive, are in Sciara reynoldsi Metz (METZ, in press). Selective segregation of chromosomes has previously been established in three species of Sciara (METZ 1926, 1928, 1929). The present paper establishes selective segregation in two other species; namely, S. ocellaris and S. reynoldsi. The dominant characters were found by the second author among the descendants of flies which had been exposed to radium. The radiation was done a t the Howard A. Kelly Hospital in Baltimore through the kindness of Dr. FRED WEST, to whom we are greatly indebted. Whether the mutations were produced as a result of the radiation cannot be stated definitely, TABLE I Linkage data for the character “Stop” in S . coprophila.

Effects of a Compound Duplication of the X Chromosome of Drosophila Melanogaster.

Abstract: OBZHANSKY (1934) has described effects on crossing over and D disjunction of duplicating fragments of the X chromosome of Drosophila melanogaster. He has found that fragments partially suppress crossing over between the entire X’s and that the effect is correlated with the length of the fragment. Some of the fragments were free and controlled by their own spindle fiber attachments and some others were attached to an entire X chromosome at the spindle fiber end. Duplication IOO described here differs in length and in composition from those described in DOBZHANSKY’S study; the results are thus largely an extension of his results. The study was undertaken especially for a comparison of the effects of the same fragment in both states, when free and when attached to an entire X. Some effects of a Y chromosome in different combinations of two X’s and the fragment have been observed.