Positional Cloning Of The Nb Gene

Silkworm is not only an important economic insect but also a good genetic research material which has plentiful mutants resource.About 1.000 mutants have been preserved worldwide.In the century of genetic research.about 400 mutants were mapped in all the 28 linkage groups,while the RFLP.RAPD.AFLP.SSR.SNP maps of silkworm were also completed.About 30 mutants' molecular genetic mechanism were well stated.Especially in recent years.The technology of positional cloning shows outstanding result in molecular genetic research of the muntants in silkworm.The genes of fl.nsd-2.ow.bts.C.mln have been found by this technology.nb is one of some body shape mutannts in silkworm.The breast of the nb is narrow.which has been mapped in the 19-31.2 loucus.In this research we used dazao and nb as parental strain to produce BC1 population.By selecting the SNP marker we carried out the positional cloning of nb and got some results as follow:1.Construction of nb's low-density map21 primer sets were disigned for rough mapping.which include 21 SNP primer sets and 6 SSR primer sets in the 21 sets.We obtained 14 sets which could be used for mapping after screening.By Using ten of these markers and 92 BC1 individuals.we constructed an low-density linkage map.The map contains 40 exchanged individuals.Through analysis.The nb-linked region was narrow to the 1.7Mb range on chromosome 19 between two SNP markers.3 and 8.The genetic distance between the two markers is 7.8cM.2.Construction of nb's high-density mapWe designed 15 novel SNP primer sets for fine mapping.and 13 out of 15 sets could be used for fine mapping.By using the rough mapping markers 3 and 8 to screen for the exchanged individuals.we have got 67 exchanged individuals from 1794 BC1 individuals which could use in the fine mapping.Subsequently.We selected 9 of the 13 markers and 67 individuals to construct the high-density linkage map.The map contains 54 exchange individuals.Through analysis.The nb-linked region was further narrow to the 1Mb range between two SNP markers.31 and 38. 3. Prediction and information analysis of genes in the regionBy gene prediction in this region.we found that the region contains 44 genes.Functional annotation and microarray gene expression analysis shows that there are 30 genes which have functional annotation and 30 genes which express during the third day of five instar period.Through clusting into groups.21 genes which are the most part of genes have the binding function.There are 11 gene express during the third day of 5th instar.We aslo analysis the structure and homolog gene of the eleven genes.