Could not complete log in. Possible causes and solutions are:
Cookies are not set, which might happen if you've never visited this website before.
Please open https://media.dlib.indiana.edu/ in a new window, then come back and refresh this page.
An ad blocker is preventing successful login.
Please disable ad blockers for this site then refresh this page.
Portrays the frequency of a mutant in the gene pool as reaching a state of equilibrium when, per generation, its origination by mutation equals its elimination by genetic death. Discusses genetic death and presents examples of how genetic loads are changed subsequent to radiation exposure. Pictures the great majority of mutants as harmful when homozygous, but some cases, as in sickle call anemia, heterozygotes are adaptively superior to normal homozygotes. Explains balanced polymorphism, by which a gene is retained in the population despite its lethality when homozygous because of the advantage it confers when heterozygous. Lectures given by Dr. Thomas Dobzhansky.
Discusses the role of heredity and environment in determining the sex of various organisms. Indicates that in some organisms it is the environment in which a given genotype functions that determines whether differentiation shall occur as male or as female. This is exemplified by sex determination in certain snails, mosses, and worms. Portrays a difference in genetic constitution as primarily responsible for sex determination in other organisms as for a unicellular plant (Chlamydomanas), certain grasshoppers, Drosophila, man, and the mouse. Discusses the genetic basis for sex mosaics (gynandromorphs) and indicates the influences of the "y" chromosome in determining sex in man. Lecture by Dr. C. Stern.
Portrays sex as a polygenic trait which may be considered to be determined by the balance of genes on different chromosomes. This view is substantiated by the work of R. Goldschmidt on the gypsy moth and its intersexes, and is most clearly demonstrates in Bridges' studies of different sex types in Drosophila. Discusses sex determination and the role of hormones in sex differentiation in the case of man. Depicts the human sex ratio and the cause of significant deviations in it from normality, and discusses the possibility of controlling sex by separating male and female producing sperm. Lecture by Dr. C. Stern.
Technique of drilling and tapping blind holes in cast steel on a radial drill. A drill jig with loose bushings is used for locating the holes. Setting up the work on the table of the machine, setting the jig on the piece to the layout lines. Calculating the size of the tap drill and the method used when setting the machine to drill a number of holes to the same depth. A wizard drill chuck is used in the drilling operation, and a standard friction chuck for holding the tap. The action of a tap in a hole is shown in animation and the reason why a tap binds in the hole and must be reversed frequently when tapping in tough metals.
Division of Visual Aids, U.S. Office of Education, Federal Security Agency, Ray-Bell Films, Inc.
Summary:
Shows how to assemble broaching inserts in right- and left-hand toolholders, how to mount and adjust toolholders in the double ram; how to mount and adjust the work fixtures; how to set trip dogs for the ram stroke; how to measure the workpiece after trial broaching; and how to surface-broach on a double ram vertical broaching machine at a production rate.
Shows various types of micrometers; how to use a micrometer, read the barrel and thimble scales, check the accuracy of readings, and take care of the instrument.
The third film in a five-film series, this film illustrates how pre-school children use the forms and arrangements of the words of their language to convey meaning. This is the grammar of the language. This film shows how patterns of organization differ from language to language and are based not so much on logic as on customs and conventions peculiar to each language. A class in German shows how grammatical patterns and their variations are taught by modern methods.
University Films, J. D. Watson, Irwin H. Herskowitz
Summary:
Describes RNA and DNA which are favored as the carriers of genetic information. Presents DNA molecules as shown in the electron microscope and describes the polymeric nature of the DNA molecule and DNA nucleotides. Compares the base content of DNA from various organisms. Describes in detail the three-dimensional organization of DNA as revealed through X-ray diffraction experiments. Pictures a Watson-Crick double helix model of DNA which suggests that DNA may replicate by the two complementary chains separating with each single strand then acting as a template to form its complement. Lecture given by Dr. J. D. Watson.
Describes the ways in which genes produce phenotypic differences by acting very early in embryonic development. Shows that this action may take place at a distance through chemical messengers (pituitary dwarfism in the house mouse, lethal giant larva in Drosophila), or it may involve tissue induction systems (Brachyury and taillessness in the house mouse). Discusses the development of eye color in Drosophila as a model of how each of the steps in a chain of chemical processes leading to development is under genic control. Lecture given by Dr. L. C. Dunn.
Portrays the role of developmental genetics in dealing with ways phenotypes come into being through the action of genes. Presents a complete discussion of the Creeper domestic fowl--its genetic basis, morphology, embryological history, and the experimental work that led to an understanding of how this gene affects early development to produce the morphological features seen as the outcome of the developmental process. Lecture given by Dr. L. C. Dunn.
Shows the parts of a single ram vertical machine; how to interpret the blueprint of a broaching tool; how to install broaching inserts for straddle broaching; how to mount the toolholder with its assembled broaching tool; how to mount and adjust the work fixture; and how to surface-broach at production rate.
Pictures reproductive isolation originating through interspecific hybridization, via amphyploidy (radish-cabbage, new world cottons, goatsbeard species), and by means of introgression (tobacco, rose family, maize-teosinte), and by the direct recombination of the products of crossing and the establishment of recombinations (larkspur). Specifies ways in which natural selection can aid reproductive isolation directly or indirectly. Depicts hybridization as a powerful stimulus in species formation and as a valuable experimental tool for the study of the genetic basis for species differences. Lecture given by Dr. G. L. Stebbins.
Demonstrates independent segregation by different pairs of genes using Mendel's data. Emphasizes the chromosomal activities during meiosis which are responsible for independent segregation. Describes the Punnett Square and the branching track methods of combining gametes at random. Discusses test crosses and linkage (as the exception to independent segregation), and shows that independent segregation proves the separability of the germ plasm into many gene pairs. Depicts the role of genetic recombination in speeding the process of evolution. Lecture by Dr. E. Altenburg.
Discusses the effect of various levels of inbreeding (self-fertilization, sib matings, half-sib matings, cousin marriages) upon making heterozygous genes homozygous with the consequent loss of vigor. Presents data for the increased risk of genetic defect from cousin marriage in studies of phenylketonuria, of a Japanese population and a French population. The concept and estimation of lethal equivalents are given. Shows how increases in heterozygosity increase vigor (heterosis); hybrid vigor in corn in described in detail. Lecture given by Dr. J. F. Crow.
Portrays the frequency of mutants in the population gene pool as dependent upon their rate of origination and selection coefficient. Discusses the population fate of dominant lethals (retinoblastoma), dominant detrimentals (achondroplasia), and recessive lethals (juvenile amaurotic idiocy). Describes in detail the loads of mutations carried in natural populations of Drosophila pseudo obscura and in man. Points out the fact that while most mutants are detrimental in the normal environment of the species, some may be advantageous in a different environment. Lecture given by Dr. Th. Dobzhansky.
Demonstrates through slow motion and natural photography the positions and movements of the "Hoosier Promenade." Opens with a group of eight dancers performing the introduction to the dance. Shows each pair of dancers, identified by a number, demonstrating the different parts of the dance and how each step flows smoothly into the next. Concludes with the performance of the dance to a record.
Uses animation, slow motion, and real photography to demonstrate the positions and movements of dancers and dancing couples in the "grapevine twist." Shows each part of the dance separately and then shows how each step flows smoothly into the next as the dancers perform to synchronous music.
Teaches the square dance figure "Take a Little Peek," with synchronous music and action. Presents live and animated demonstrations of the dance at regular speed and in slow motion, and explains the positions of partners, how to honor corners and partners, and how the steps are performed to facilitate the continuity of the dance. Pictures groups dancing the figure to regular square dance music in a natural situation.
Demonstrates through slow motion and natural photography the positions and movements of the "Texas Star." Opens with a group of eight dancers performing the introduction to the dance. Shows each pair of dancers, identified by a number, demonstrating the different parts of the dance and how each step flows smoothly into the next. Concludes with the performance of the dance to a record.
Demonstrates various methods of preparing materials to be used on different types of still projectors. Explains that instructional materials may be prepared for projection by utilizing their qualities of opacity, translucency, and transparency. Shows the use of carbon film, adhesive coloring materials, India ink, and sheets of plastic. Demonstrates a technique for stenciling on carbon film and a method for making plastic transparencies from magazine pictures.
