<P> Since the 1920s, a number of sex determination models have been proposed for Cannabis . Ainsworth describes sex determination in the genus as using "an X / autosome dosage type". </P> <P> The question of whether heteromorphic sex chromosomes are indeed present is most conveniently answered if such chromosomes were clearly visible in a karyotype . Cannabis was one of the first plant species to be karyotyped; however, this was in a period when karyotype preparation was primitive by modern standards (see History of Cytogenetics). Heteromorphic sex chromosomes were reported to occur in staminate individuals of dioecious "Kentucky" hemp, but were not found in pistillate individuals of the same variety . Dioecious "Kentucky" hemp was assumed to use an XY mechanism . Heterosomes were not observed in analyzed individuals of monoecious "Kentucky" hemp, nor in an unidentified German cultivar . These varieties were assumed to have sex chromosome composition XX . According to other researchers, no modern karyotype of Cannabis had been published as of 1996 . Proponents of the XY system state that Y chromosome is slightly larger than the X, but difficult to differentiate cytologically . </P> <P> More recently, Sakamoto and various co-authors have used RAPD to isolate several genetic marker sequences that they name Male - Associated DNA in Cannabis (MADC), and which they interpret as indirect evidence of a male chromosome . Several other research groups have reported identification of male - associated markers using RAPD and AFLP . Ainsworth commented on these findings, stating, </P> <Table> <Tr> <Td> "</Td> <Td> It is not surprising that male - associated markers are relatively abundant . In dioecious plants where sex chromosomes have not been identified, markers for maleness indicate either the presence of sex chromosomes which have not been distinguished by cytological methods or that the marker is tightly linked to a gene involved in sex determination . </Td> <Td>" </Td> </Tr> </Table>

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