A possible influence of the spindle fibre on crossing-over in Drosophila

The distribution of genes in the second and third chromosomes of Drosophila melanogaster suggests that crossing-over may be influenced by the spindle fibre at least in neighboring regions. The disparity between the genetic and cytological maps of these chromosomes especially in the spindle fibre regions (Dobzhanzky 2,3) is consistent with such a view

Development of eye colors in Drosophila: some properties of the hormones concerned

The substance inducing the production of pigment in the eyes of vermilion brown mutants of Drosophila melanogaster has been shown to be a relatively stable chemical entity possessing true hormone-like activity. A simple method for obtaining hormone solutions has been developed involving extraction of dried wild type Drosophila pupae with ethyl alcohol and water. A logarithmic proportionality has been found to exist between the amount of hormone and the induced eye color. This relationship provides a simple method for the quantitative determination of hormone concentration in given extracts. Larvae and pupae of D. melanogaster contain an intracellular enzyme which inactivates the hormone in the presence of molecular oxygen. The hormone is not oxidized under ordinary conditions with either molecular oxygen or hydrogen peroxide. The hormone has been found to be an amphoteric compound with both acidic and basic groups and with a molecular weight between 400 and 600. The solubility and precipitation reactions of the hormone suggest its amino acid-like nature. However, the instability to heat, acid, and alkali, and its rather restricted occurrence indicate a rather complex specific structure

Development of Eye Colors in Drosophila: Extraction of the Diffusible Substances Concerned

The development of eye color in Drosophila is known to involve special diffusible substances [1,2]. A genetically vermilion (v) eye will develop wild-type eye color if it is supplied with v+ substance by transplantation or by injection of body fluid of wild type flies. Similarly a genetically cinnabar (cn) eye will develop the color characteristic of wild type if it is supplied with cn+ substance. The present paper summarizes preliminary experiments made to learn something of the nature of the two substances just mentioned. During the course of our studies, Ephrussi and Harnly [3] have shown that pupal fluid can be freed of living cells by freezing in liquid air without destroying the v+ and cn+ substances. Khouvine, Ephrussi and Harnly [4] have shown further that these substances can be extracted from Calliphora pupae with 95 per cent alcohol-ether mixtures and with 95 per cent alcohol but not with pure ether. They conclude that these substances are not proteins or enzymes, a conclusion confirmed by our work

A microbiological method for the determination of choline by use of a mutant of Neurospora

Previous communications from this laboratory have described the production of biochemical mutants in the mold Neurospora by means of ultraviolet and x-rays (1, 2). Such mutants are characterized by the inability to carry out specific chemical syntheses which normally occur in the unmutated, or wild type, strain. In each case which has been genetically analyzed the failure of the synthesis has been found to be related to the mutation of a single gene. The strain to be described, known as No. 34486, or cholineless, arose from a culture of wild type Neurospora crassa which had been irradiated with ultraviolet light. It was found to be unable to grow in a medium containing only salts, sugar, and biotin, but it grew normally on the addition of a mixture of water-soluble vitamins. When the components of the mixture were tested singly, it was found that the addition of choline alone permitted normal growth. Up to the present, no completely satisfactory method for the determination of choline in natural products and tissue extracts has been described. Chemical methods, such as precipitation of the reineckate, lack specificity, while the biological method of Fletcher, Best, and Solandt (3) is time-consuming and difficult, and “possesses many dangerous pitfalls for the chemist” (4). The whole subject has been critically reviewed by Best and Lucas (4). It was therefore of interest to determine whether the Neurospora mutant is a suitable test organism in a quantitative assay for choline. The experiments to be described show that this is the case and form the basis of a simple, sensitive, and specific method for the determination of choline in natural products. By this procedure it is possible to determine choline in a concentration of 0.02 mg. per liter; routine analyses can be run on 100 mg. samples of material

Comments on Bernard O. Dodge

Comments on Bernard O. Dodg

Physiological Aspects of Genetics

In its concern with the physical, chemical, and biological nature of the specifications which living systems transmit from one generation to the next, genetics has come to play a central role in modern biology. Progress is being made so rapidly that it is almost impossible for a single individual to keep abreast of advances on all fronts. This review is prepared for physiologists and others who are not primarily specialists in genetics. It will attempt to survey in a general way some of the advances that seem to the author to be of particular interest and importance. In no sense wilI it cover all of significance in genetics that has happened in the three years since the preparation of the previous review of genetics for this series (1). Fortunately a number of excellent summaries of progress in particular branches of genetics have recently appeared or are in preparation. These, rather than more technical papers, will often be cited as convenient sources of additional information. Pontecorvo’s Jesup Lectures (2) provide an excellent survey of newer approaches to genetic analysis. Ravin (3) and Wheeler (4) have recently viewed work on the genetics of bacteria and fungi, and Levinthal has surveyed the general situation, especially for physicists and other non-geneticists (5). Fincham (6) has in press a summary of the genetics of enzyme activity