Most sex linked genes are found on the

The student of the humanities as well as the intelligent public looks at the history of human thought as a history of abstract ideas. It is true that minds like those of Plato, Thomas Aquinas, Spinoza, Descartes, Hegel and Kant have exercised a strong influence upon the progress of thinking in all spheres, even upon the actual course of most sex linked genes are found on the events.

When future historians turn to examine the major intellectual accomplishments of the twentieth century, they will undoubtedly give a special place to the extraordinary achievements in biology, achievements that have revolutionized our understanding of life’s processes and of disease. Important intimations of what was to happen in biology were already apparent in the second half of the nineteenth century. Thomas Hunt Morgan was born in Kentucky in 1866 to a distinguished southern family whose members included Francis Scott Key. Morgan was trained as a developmental biologist, receiving his Ph. 1890 from the Johns Hopkins University for work on the development of sea spiders, a specialized group of invertebrate animals, and in 1891 he accepted a teaching post at Bryn Mawr College. But Morgan persisted, and in April 1910 he suddenly had a breakthrough. In one of his bottles filled with Drosophila was a male fly with rather than the normal red eyes.

How did this white eye color originate? Once this idea formed in his mind, Morgan sensed that the experimental power of the fly would allow him to understand heredity. A focus on chromosomes and their morphology was not what Morgan had in mind when he started to work on flies. As early as 1911, Morgan had redirected his research in an attempt to provide additional information about the chromosome theory of heredity, and before long he achieved another major conceptual breakthrough. Morgan also made a third contribution, a sociological one that helped introduce at Columbia and into American science as a whole a set of sweeping institutional changes. Until the start of the twentieth century, the leading American research universities -Harvard, Johns Hopkins, Columbia, and Chicago- had all been inspired by the model of the German research university, in which the Geheimrat, the great scientific leader, ordered the hierarchy of his subordinates. The atmosphere in the Fly Room was described by Sturtevant, one of the youngest in the group.

He wrote: “This group worked as a unit. Each carried on his own experiments, but each knew exactly what the others were doing, and each new result was freely discussed. There was little attention paid to priority or to the source of new ideas or new interpretations. What mattered was to get ahead with the work.

I have benefited from the comments on this essay by Garland Allen, Norman Horowitz, Tom Jessell, Joshua Lederberg, E. Lewis, Robert Merton ’85HON, Gary Struhl, Andrew Tomlinson, and Harriet Zuckerman ’65GSAS. As pointed out by Harriet Zuckerman, this view was not shared by Muller, who stood further away from the group than the rest and thought that his own contributions had not been fully recognized: see Zuckerman, 1977, pp. Thomas Hunt Morgan: The Man and His Science. Embryology and Its Relations,” Science 85:369-374. Thomas Hunt Morgan: Pioneer of Genetics. The haploid stage of a plant exhibiting alternation of generations, generates gametes by the process of mitosis.

Junctions between the plasma membranes of animal cells that allow communication between the cytoplasm of adjacent cells. The folds and grooves into which the stomach lining is arranged. A hormone produced by the pyloric gland area of the stomach that stimulates the secretion of gastric acids. A ring of muscle at the junction of the esophagus and the stomach that remains closed except during swallowing to prevent the stomach contents from entering the esophagus. The sum of all the genetic information carried by members of a population. Note: there is no diving in the deep end of the gene pool!

Sequence of DNA bases usually code for a polypeptide sequence of amino acids. The linear series of nucleotides, read as triplets, that speciÞes the sequence of amino acids in proteins. The separation of a population’s gene pool from the gene pools of other populations due to mutation, genetic drift, and selection. Continued divergence can lead to speciation. The study of the structure and function of genes and the transmission of genes from parents to offspring.

The set of genes carried by an individual. The set of genes shared by members of a reproductive unit such as a population or species. The total area occupied by a population. Plants’ response to gravity: roots grow downward, showing positive geotropism, while shoots grow upward in a negative response. Collective term for cells in the reproductive organs of multicellular organisms that divide by meiosis to produce gametes.

Period of time between fertilization and birth of an animal. A group of hormones that stimulate cell division and elongation in plants. GA is also applied to certain plants to promote larger fruits. Opening or clefts between the gill arches in Þsh.