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Joined 2026-09-21 Message
Incoming links: X chromosome
Ronald J. Konopka 2026-11-05
Ronald J. Konopka coauthored the 1971 identification of circadian rhythm mutants in Drosophila melanogaster with Seymour Benzer. Their screen produced arrhythmic, short-period and long-period flies. The combination showed that a mutation can alter the period of an internal timing mechanism, rather than only disabling movement altogether.[ref]
Clock Mutants of Drosophila melanogaster by Ronald J. Konopka and Seymour Benzer. Abstract: arrhythmic, 19-hour and 28-hour phenotypes
Automatic collection measured when adults emerged, and infrared detectors measured individual locomotion. Tests in constant darkness separated free-running timing from direct light-driven activity. Mapping and complementation indicated that the three mutations affected the same functional gene on the X chromosome, providing an entry point for the genetics of biological clocks.[ref]
Clock Mutants of Drosophila melanogaster by Ronald J. Konopka and Seymour Benzer. Printed pp. 2112–2115, apparatus and genetic analysis
Seymour Benzer 2026-11-05
Seymour Benzer helped turn the study of behavior into an experimental problem in genetics. With Ronald J. Konopka, he reported fruit-fly mutations that abolished daily rhythmicity or changed its period to approximately 19 or 28 hours. Both adult emergence and individual locomotor activity were affected.[ref]
Clock Mutants of Drosophila melanogaster by Ronald J. Konopka and Seymour Benzer. 1971, abstract and printed pp. 2112–2113
Flies were tested in constant darkness, while infrared monitoring recorded individual movement without imposing a daily light cycle. Persistence of altered timing under those conditions supported an internal circadian rhythm mechanism, rather than merely a different immediate response to the lamps switching on. The mutations mapped to the same functional gene on the X chromosome.[ref]
Clock Mutants of Drosophila melanogaster by Ronald J. Konopka and Seymour Benzer. Materials and Methods, locomotor apparatus; Results, mapping and complementation
Portrait of Seymour Benzer
. Caltech photograph identifying Benzer beside an enlarged fruit-fly model. Source. X chromosome 2026-11-05
The X chromosome is a sex chromosome in the human and many other mammalian chromosome systems. Typical human XX cells contain two copies and typical XY cells contain one. Many genes on the X chromosome participate in functions beyond sex determination, so its inheritance can influence a wide range of phenotypes.[ref]
For an illustrative recessive allele in a region without an equivalent functional copy on the Y chromosome, an XY individual has only the one X-linked copy at that location. An XX individual can carry another allele on the other X chromosome, although X-chromosome inactivation and other biological details affect expression. Thus “recessive” describes a relationship between alleles when both are present; it does not make a single inherited copy biologically invisible. The example explains an inheritance pattern without making every trait on the X chromosome follow one simple rule.