Alteration of fish melanic characteristics following transfer of total DNA

309 Using a CE-450 cell fusionor or a polarizer-injector-I, a DC pulse (20-160 ps, loo-250 V) was applied to both sides of first cleavage stage embryos with chorion of grass carp, common carp and rainbow trout. The fusion process of the two embryonic cells at the animal pole could be seen for grass carp and common carp. About one third of the treated eggs died soon, one third developed into deformed fry and one third developed normally. One hundred days after the treatment, the DNA content of red blood cells of the normally developed fish was measured using a cytophotometric microscope. Among 2 1 rainbow trout, some were mosaic with diploid, triploid and aneuploid cells, while the remainder were the same as the control without change in ploidy. Six of ten grass carp were mosaic with diploid, triploid, tetraploid and aneuploid cells and one of the ten was tetraploid. Of 22 common carp analyzed, some were mosaic with increased DNA content, but most were aneuploid with a reduced DNA content in the red blood cells. Thus, the electrofused cells of fish embryos may develop in the following ways: cells again divide to form diploid cells; no chromosome exclusion occurs and the fusion cell develops into a tetraploid, chromosome exclusion of the fusion cells occurs to varying degrees so that aneuploid cells between diploid and tetraploid cells are found frequently; and some individuals have a DNA content lower than the control without any morphological difference. This might be caused by chromosome exclusion removing some of the self chromosomes.

Alteration of fish melanic characteristics following transfer of total DNA

Guo Wen, Liu Hanqin, Wang Tiehui and Chen Hongxi Department of Fish Genetics and Breeding, Institute ofHydrobiology, The Chinese Academy of Sciences, Wuhan, Hubei 430072, China

Total DNA (about 30 kb) isolated from Japanese phytophagous crucian carp (Carassius auratus cuvieri) liver was transferred by microinjection into fertilized eggs of red carp (Cyprinus carpio red var. ) . The DNA was prepared in two concentrations. The melanin expression during embryo development was chosen as a selective marker of transgenic fish. Six of 438 microinjetted red carp fry survived microinjection and all showed similar melanin expression to that of crucian carp which resulted from gene transfer. The result indicates a possible new way of improving fish characteristics. A possible mechanism of foreign DNA integration into the genome of recipient eggs is homologous recombination between foreign DNA and the chromosome DNA of the recipient eggs.