|Appears in Collections:
|Analysis of sex determination in Nile tilapia (Oreochromis niloticus L.): a molecular genetics approach
|Ezaz, Md. Tariq
|Penman, David J.
McAndrew, Brendan J.
chromosome set manipulations
|University of Stirling
|Ezaz MT, Harvey SC, Boonphakdee C, Teale AJ, McAndrew BJ and Penman DJ (2004) Isolation and physical mapping of sex-linked AFLP markers in the Nile tilapia (Oreochromis niloticus L.). Marine Biotechnology 6: 435-445.
Ezaz MT, Sayeed S, McAndrew, BJ and Penman DJ (2004) Use of microsatellite loci and AFLP markers to verify gynogenesis and clonal lines in Nile Tilapia (Oreochromis niloticus L.). Aquaculture Research. 35: 1472-1481.
Ezaz MT, McAndrew BJ and Penman DJ (2004) Spontaneous diploidization of maternal chromosome set in Nile tilapia (Oreochromis niloticus L.) eggs. Aquaculture Research 35: 271-277.
Ezaz MT, Myers J, Powell SF, McAndrew BJ and Penman DJ (2004) Sex ratios in the progeny of androgenetic and gynogenetic YY male Nile tilapia, Oreochromis niloticus L. Aquaculture 232: 205-214.
Karayücel I, Ezaz MT, Karayücel S, McAndrew BJ and Penman DJ (2004) Evidence for two unlinked “sex reversal” loci in the Nile tilapia, Oreochromis niloticus, and linkage of one of these to the autosomal red body colour gene. Aquaculture 234: 51-63.
|Seven families of XX and YY homozygous Oreochromis niloticus were produced by mitotic gynogenesis from XY neofemales and their genetic status was verified by multilocus DNA fingerprinting and progeny testing. Two of these gynogenetic families and their corresponding diploid controls were used with 64 AFLP primer combinations in different levels of screening (XX/YY grand pool; XX/YY family pool; XX/YY gynogenetics and XX/XY control individuals) to search for sex-linked or sex-specific markers. Grand pool screening did not reveal any sex-linked markers. Subsequent family pool and individual level screening identified four sex-linked AFLP markers from two primer combinations, three Y-linked (OniY425, OniY382, OniY227) and one X-linked (OniX420). Two of these (OniX420, OniY425) were shown to be allelic. Single locus PCR markers were developed for all of those markers. Linkage analysis of these markers and the sex locus within the source families revealed tight linkage, with estimated map distances of 13cM, 17cM and 20cM for OniY382, OniY227 and OniX420/OniY425 respectively. However, these sex-linked AFLP markers failed to consistently identify sex in unrelated individuals. To develop an effective system for parentage analysis in normal and gynogenetic progeny, AFLPs and multiplexed polymorphic microsatellite loci were investigated. Both were found to be effective, but microsatellites were more appropriate since they are codominant and some loci showed high gene-centromere recombination rates, suitable for discriminating meiotic from mitotic gynogenetics, while AFLPs are dominant markers. Spontaneous diploidization of the maternal chromosome set (SDM) was observed in gynogenetic progeny of one XY neofemale. Maternal inheritance and ploidy status were verified by multilocus DNA fingerprinting and chromosome karyotyping. Close genetic linkage between the red gene and an autosomal sex-reversal gene(s) in gynogenetic progeny and influences of autosomal sex-reversal gene(s) producing males in a fully inbred XX clonal line were previously reported in O. niloticus. To test if the same autosomal sex-reversal locus was responsible in both cases, a series of test crosses was carried out involving XX clonal neomale(s) and homozygous red females. The results indicated the involvement of more than one autosomal sex-reversal locus, one of which is linked to red body colour.
|Thesis or Dissertation
|School of Natural Sciences
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