Genetic mapping by molecular markers with gametic and genotypic segregation distortion / Mapeamento genético utilizando marcadores moleculares com distorção de segregação gamética e genotípica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The development of the genetic maps based on DNA markers has been providing remarkable progresses to the genomics of plants and animals. The construction of a genetic map is performed, by using data from the segregant populations, that usually are backcrossing, F2 generation, RILs, double-haploids and others. A mendelian segregation pattern that is typical to each population and makes possible to foresee genotypic relationships, as well as to estimate recombinations from the presuppositions within the probabilistic models is expected for each marker. The obsence of the mendelian segregation pattern is so-called segregation distortion (DS), that may affect the statistical tests used to detect the linkage as well as to generate positive falses in a genetic map. Taking into account the problems the DS may cause in relation to the construction of the genetic linkage maps, this study is concerning to the themes on the detection, effects and implications of DS in the establishment of accurate genetic maps. It was found that genotypic DS is more prejudicial than gametic DS. The estimative values of the distances among marks even with gametic DS are biased when neglecting the distortion, mainly with more distant levels of segregation ratio than the expected segregation. Due to those verifications, some likelihood functions taking into account the gametic DS for the backcrossing populations, F2 generation, RIL and double-haploid were developed. In addition, two strategies were proposed for using these likelihood functions. In the first strategy, it is presupposed that the marks presenting segregation distortion and also the expected rate are known, so the value of the DS rate could be assumed as a parametric one. In the second strategy, the value of the DS rate is estimated from the observed data concerning to the markers under study. Then, this value is used for calculating the value of the distance between the markers i and i . As for the marker i the distortion rate will be given by si and the marker i inhibits a distortion rate si , two estimates of the recombination percentage measure between i and i are obtained, whereas the distance value is the mean estimate.

ASSUNTO(S)

biologia molecular chromosome mapping breeding marcadores genéticos melhoramento genético genetics biologia molecular mapeamento cromossômico molecular markers genética molecular biology

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