RESUMEN
Two alleles are encoded at the malate dehydrogenase locus in largemouth bass, Micropterus salmoides. Populations in the extreme northern areas of the range of this fish are fixed or nearly fixed for the B1 allele, whereas populations in Florida are fixed for the alternative allele, B2. The MDH-B1B1 and MDH-B2B2 allelic isozymes were isolated by preparative starch gel electrophoresis and subjected to in vitro kinetic analyses. The apparent Km (oxaloacetate) for each of these allelic isozymes was determined at 25, 30, and 35 degrees C. The Km values for both isozymes increased with increasing temperature and were not significantly different from each other at 25 and 35 degrees C. However, at 30 degrees C the Km value for the MDH-B1B1 allelic isozyme was higher than that for the MDH-B2B2 isozyme (i.e., 5.4 X 10(-5) vs 3.3 X 10(-5)). These results are consistent with the hypothesis that the different environmental temperatures at different latitudes may be at least partially responsible for the north-south cline in Mdh-B allele frequencies.
Asunto(s)
Peces/genética , Isoenzimas/genética , Malato Deshidrogenasa/genética , Animales , Peces/metabolismo , Calor , Isoenzimas/metabolismo , Cinética , Malato Deshidrogenasa/metabolismoAsunto(s)
Peces/embriología , Hibridación Genética , Isoenzimas/genética , Animales , Creatina Quinasa/genética , Peces/genética , Glucosa-6-Fosfato Isomerasa/genética , L-Lactato Deshidrogenasa/genética , Malato Deshidrogenasa/genética , Modelos Biológicos , Fosfoglucomutasa/genética , Fosfogluconato Deshidrogenasa/genética , Superóxido Dismutasa/genéticaRESUMEN
The purpose of the present investigation is to determine whether the two duplicated glucosephosphate isomerase (EC 5.3.1.9) loci Gpi-A and Gpi-B reside on the same chromosome in teleostean fishes. Interspecific sunfish hybrids were employed for the cross because of the different species-specific electrophoretic mobilities of the allelic isozymes at each GPI locus and because of their genomic compatibility. F1 sunfish hybrids, formed from a male warmouth (Lepomis gulosus) X female green sunfish (L. cyanellus) cross, were mated to form the F2 generation. The number of each of the nine different isozyme phenotypes, revealed by starch gel electrophoresis, was determined using 256 F2 individuals. The high frequency of recombinant phenotypes in the F2 generation indicated that the two GPI loci are not linked. An excess of F2 individuals heterozygous at both loci was observed and is interpreted as being caused by heterosis. The absence of linkage for the homologous loci encoding GPI subunits and for other multilocus isozyme systems is consistent with the postulate that the genomes of present-day vertebrates arose through one or more polyploidization events early in vertebrate evolution.
Asunto(s)
Peces/metabolismo , Genes , Ligamiento Genético , Glucosa-6-Fosfato Isomerasa , Isoenzimas , Animales , Mapeo Cromosómico , Cromosomas , Cruzamientos Genéticos , Hibridación Genética , FenotipoAsunto(s)
Peces/metabolismo , Heterocigoto , Hibridación Genética , Alelos , Animales , Peso Corporal , Mapeo Cromosómico , Cruzamientos Genéticos , Electroforesis en Gel de Almidón , Ojo/enzimología , Femenino , Agua Dulce , Frecuencia de los Genes , Genética de Población , Genotipo , Homocigoto , Vigor Híbrido , Isocitrato Deshidrogenasa/metabolismo , Isoenzimas/metabolismo , L-Lactato Deshidrogenasa/metabolismo , Hígado/enzimología , Malato Deshidrogenasa/metabolismo , Masculino , Músculos/enzimología , Fenotipo , Factores de TiempoRESUMEN
Backcross hybrids produced from the bluegill, the red-ear sunfish, and their F(1) interspecific hybrid have been analyzed for the inheritance of six enzyme phenotypes. Malate dehydrogenase A and B, tetrazolium oxidase, 6-phosphogluconate dehydrogenase, skeletal muscle esterase, and liver alpha-glycerophosphate dehydrogenase are all inherited in a mendelian manner as codominant alleles at nuclear loci. 6-phosphogluconate dehydrogenase and alpha-glycerophosphate dehydrogenase are encoded by linked loci, undergoing recombination at a frequency of 15%-22%. No other case of linkage was observed. The absence of linkage between the homologous malate dehydrogenase loci is of particular interest. These interspecific hybrids appear to be very useful for studies of biochemical genetics.