Application of RAPD and cytochrome b sequences to the study of genetic variations in F-1 and F-2 generations of two different strains of guppy (Poecilia reticulata, Peter 1854)

摘要

The DNA of two laboratory strains of guppy (Poecilia reticulata), Black Yellow (BYS) and Red Flame (RFS), was studied with respect to their colour differences, in two generations (F-1 and F-2). Their varying morphological colours were related to their cloned fragments of cytochrome b mitochondrial DNA (mtDNA) and random-amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The F-1 generation was characterized by various forms. The male BYS could be divided into 68% having black-yellow tails and 14% having black-yellow-red tails. The other variations were found in very low percentages. The percentage of black-yellow-tailed males increased to 85 in the F-2 generation, and the percentages of the various other forms consequently decreased. Only 63% of BYS males had black-yellow dorsal fins in the F-1 generation, but this percentage increased to 84 in F-2. Compared with the males, fewer variations were found in female colour patterns in the F-1 generation. A high percentage of BYS females (81%) colour was found with no significant increase in the F-2 generation. However, variations decreased in the F-2 females. On the other hand, a very high variation was found in female fins in the F-1 generation: only 32% were of BYS colour and 25% had no-colour fins. However, a significant increase in BYS colour was found in the F-2 generation (61%) and 39% had no colour. The variation in RFS was lower than BYS in the F-1 generation: 81% of the F-1 males had red-yellow tails with colour, 46% of the fins were yellow and 36% were red-white. In females, a very high percentage (84%) had red-yellow tails and 76% had no-colour dorsal fins. Mitochondria DNA markers and genomic DNA were studied in various laboratory strains. In the clone of the fragments of cytochrome b, the bands correlated to the colour phenotype. A fragment of the cDNA sequence was determined from a 268-bp cloned with fragments of the guppy cytochrome b mtDNA gene. The genes varied for the two strains in only two base pairs, starting at the nucleotide position 171 and ending at position 174. Three primers showed good results in the RAPD-PCR and were found suitable for the study of DNA variations in guppy. The high variation detected in BYS, in comparison with RFS, was reflected by changes in band-sharing (BS) values ranging from 0.66 to 1, versus 0.8 to 1 in RFS.