G. W. Beadle

A Technique of Transplantation for Drosophila

A technique of transplantation, applicable to Drosophila species, which consists of injection by means of a micro-pipette, is described in some detail.

Genic Control of Biochemical Reactions in Neurospora

THE task of physiological genetics is that of describing gene action in chemical terms. Any such description implies, in the first place, knowledge of the chemical structure of the gene, and, in the second place, an understanding of the relationship between this chemical structure and its cellular environment. Already the first rough outlines of gene structure have been drawn. Terms such as nucleic acid, polypeptide chain, prosthetic group and crystalline virus have by now found comfortable places in the genetical vocabulary. It is the second aspect of the general problem that is the subject of the discussion this afternoon, however, and more particularly, that phase of it dealing with the role of the gene in the physiology of the organism. There is recorded in the literature a sufficient number of instances of mutations affecting the normal biochemistry of the organism to indicate that the gene exercises an important function in metabolism. The loss, through gene mutations, of the ability to form coat color pigments in mammals (Wright, 1941) and eye color pigments in Drosophila (Ephrussi, 1942) has, in particular, been investigated. Genic control of various processes involved in the production of flower pigments has also been extensively studied (Lawrence and Price, 1940). One of the clearest cases of genic control of a more or less definable chemical reaction, and also the first one to be recorded, is in the disease of mnan known as alcaptonuria (Garrod, 1923). Here the ability to oxidize hoinogentisic acid is lost, and large quantities of it are excreted in the urine. The genealogies of alcaptonurics indicate that they differ from the normal by a single recessive gene. Studies such as these have been of the greatest value in furthering our knowledge of the gene as a physiological

OVARY TRANSPLANTS IN DROSOPHILA MELANOGASTER: STUDIES OF THE CHARACTERS SINGED, FUSED, AND FEMALE-STERILE

The development of singed ovaries transplanted to wild type females in the late larval stage shows autonomous development. Eggs recovered from such females have the characteristic shape of eggs from singed females and they fail to give rise to larvae. Wild type ovaries grown in singed hosts likewise show autonomous development. Viable eggs can be recovered from such ovaries; they give rise to wild type offspring (females heterozygous for wesn) when fertilized by wesn sperm.Fused ovaries grown in singed hosts have characteristics not detectably different from such ovaries grown in their normal position. Recovered eggs fertilized by fu or by Y sperm fail to hatch, but those fertilized by not-fu X-carrying sperm give rise to normal females heterozygous for fu.Ovaries from female-sterile females grown in wild type hosts may become attached to the oviducts of the hosts, competing successfully with normal ovaries, but they remain rudimentary as they do in their normal genetic surrounding. Wild type ovaries grown...

Yellow Stripe-a Factor for Chlorophyll Deficiency in Maize Located in the Pr pr Chromosome

A Mendelian recessive chlorophyll defect in maize is described and named yellow stripe. The factor pair differentiating normal and yellow strip plants (Ys ys) lies in the Pr pr chromosome relatively close to the Pr pr locus.

Origin of Corn: Pollen Evidence

The origin of Indian corn remains controversial. Its closest wild relative is teosinte, with which it hybridizes freely to produce fertile progeny. Teosinte ears are smaller and simpler than those of corn. Searches for a more likely living ancestor have failed, but nine of its assumed pollen grains have been recovered in deep drillcore samples obtained from a stratum of soil under Mexico City, which is believed to antedate man in the Western Hemisphere. These nine largest grains are indistinguishable from pollen of modern corn. It has been assumed to be that of a postulated wild corn other than that of teosinte, but this does not account for the possibility that the pollen grains are those of a tetraploid teosinte-producing pollen with two sets of chromosomes. This likelihood has been examined by treating modern teosinte plants with colchicine, which induces tetraploidy. The result has been many teosinte pollen grains indistinguishable in size from modern corn. In interpreting thrs outcome it is important also to know that heat treatment of corn and other plants induces polyploidy, and that the deep drill-core pollen was recovered in a stratum of volcanic clay indicating the high temperature known to favor doubling of corn pollen volumes.

Development of Eye Colors in Drosophila: The Mutants Bright and Mahogany

(1) ca+ substance-a substance necessary for the development of wild type _pigment which is absent or reduced in amount in the eye color mutant claret. (2) v+ substance-a substance capable of changing the development of a vermilion eye in such a wray that it forms pigment phenotypically like that of a wild type eye. (3) cn+ substance-a substance capable of changing the development of a -cinnabar eye in such a way that it is similar in its pigmentation to a wild -type eye.

Relation of Time of Seeding to Root Development and Winter Survival of Fall Seeded Grasses and Legumes

Over much of the pasture-lands of the Great Plains area, fall seeding of small-seeded grasses and legumes is a very desirable practice. Many times it is possible to harvest a crop of small grain, and then, if weather conditions are favorable, obtain a good stand of grass or of legume, or both, the first year. Annual weeds, such as foxtail, crab-grass, and sand-burs, which usually are very common in spring seeding, are fairly well controlled if a good stand of the grass or legume is obtained in the fall. The yield the following year is usually much better than where spring seeding is practiced. On the other hand, weather conditions of this area are frequently not favorable for fall seeding. During some years the date of seeding is necessarily delayed so long by drought that not enough root development is made to enable young plants to survive the first winter. The purpose, therefore, of this study was to obtain quantitative data on the relative root development of brome grass, timothy, Kentucky blue grass, alfalfa, red clover and white biennial sweet clover, seeded at successive intervals in the fall, and to correlate this fall development with winter survival. The time of seeding, of course, varies with weather and soil conditions, species, and varieties. For this reason, careful records were kept on seasonal and soil conditions, and an effort was made to obtain well adapted strains of the grasses and legumes used. The authors realize that data collected in any one year will probably not hold for all other years, and that data covering a series of years would be more valuable. It would seem, however, that this paper might be valuable and interesting as a progress report, and might serve as an indication of what may be expected in years when similar conditions prevail.

The genetic basis of biological specificity

Abstract I shall conclude with the summary statement that it is now a widely accepted working hypothesis that the primary genetic material of higher organisms is deoxyribonuclcic acid, and that the structure proposed by Watson and Crick for this substance seems to provide a sensible chemical basis for the specificity, replication, mutation, and functioning of genetic material.

Development of eye colours inDrosophila: Studies of the mutant claret

SummaryA wilde-type eye disk transplanted to a claret host before 80 hours after egg-laying (25° C.) gives rise to an eye with pigmentation like that of claret. If the same transplantation is made shortly before puparium formation (about 106 hours after egg-laying), the resulting implant is phenotypically close to wild type. These results are interpreted by assuming that a specific diffusible substance (ca+ substance) necessary for wild-type eye colour, moves from the body to the eye in a wild-type fly during some period between 80 and 106 hours after egg-laying, and that transplantation, after this critical time, of an eye from such a fly to a host which cannot supply the substance, does not modify the normal course of pigment development.The relation of this critical time to experiments previously published is considered.Tests for the production ofca+ substance by the ovaries of wild-type flies gave negative results.