Improving QTL mapping resolution based on genotypic sampling--a case using a RIL population.

The QTL mapping results were compared with the genotypically selected and random samples of the same size on the base of a RIL population. The results demonstrated that there were no obvious differences in the trait distribution and marker segregation distortion between the genotypically selected and random samples with the same population size. However, a significant increase in QTL detection power, sensitivity, specificity, and QTL resolution in the genotypically selected samples were observed. Moreover, the highly significant effect was detected in small size of genotypically selected samples. In QTL mapping, phenotyping is a more sensitive limiting factor than genotyping so that the selection of samples could be an attractive strategy for increasing genome-wide QTL mapping resolution. The efficient selection of samples should be more helpful for QTL maker assistant selection, fine mapping, and QTL cloning.

[Genetic diversity analysis of maize recurrent selection populations by SSR marker].

Two cycles of mass (MS) and half-sib (HS) recurrent selection and one cycle of marker-assisted selection (MAS) for yield were carried out in two synthetic maize populations DC0 and XFC0, respectively. The genetic diversity of five maize (Zea mays L.) populations, including basic population DC0 and its developed populations HSC2, MSC2, and basic population XFC0 and its developed populations XFC1, were evaluated by 49 SSR primers, which are averagely distributed on 10 maize chromosomes. On the 49 SSR loci, a total of 185 alleles had been detected in these populations. At each locus, 1 to 7 alleles could be detected, with an average of 3.8. The proportion of polymorphic sites differed in the five maize populations, which were 90.3%, 85.9%, 84.9%, 85.9%, 80.5% for DC0, HSC2, MSC2, XFC0 and XFC1, respectively. Genotypes can be showed by the difference of the alleles detected on the 49 SSR loci. There were totally 430, 392, 377, 399 and 395 genotypes for DC0, HSC2, MSC2, XFC0 and XFC1, respectively. The mean gene heterozygosity calculated from the 185 alleles were 0.660, 0.644, 0.645, 0.662 and 0.655 for DC0, HSC2, MSC2, XFC0 and XFC1, respectively. All these results mean that after selection the ranges of variance of the populations decreased slightly. And the mean genetic distance calculated from the 185 alleles were 0.4695, 0.4696, 0.4698, 0.4836 and 0.4902 for DC0, HSC2, MSC2, XFC0 and XFC1, respectively. There was nearly no difference after selection in both the basic populations. Analyses on the distribution of genetic distance showed that most of the genetic distances in the developed populations were smaller than in the basic populations. But the ranges of the genetic distance were wider after selection in both populations. This result indicated that heterogeneity between some of the individuals in the developed populations increased after several times of recombination and exchange. All these indexes demonstrated that the genetic diversity of selection populations was similar to their primary populations, and genetic variation was maintained during recurrent selection.

[Study on the risk factors and its interaction on Parkinson disease].

OBJECTIVE: To explore the risk factors of Parkinson disease (PD), interaction between family history of PD and other risk factors, as well as the relative strength of genetic factors over the vulnerability of PD. METHODS: One 1:1 matched case-control study including 157 pairs of cases and controls was conducted in Qilu Hospital of Shandong University. RESULTS: Conditional logistic regression analysis showed that family history of PD, mental labor, insecticide, alcohol drinking and history of depression all had positive relationship, while smoking had a negative relationship with PD. The AP (AB)s of family history of PD and insecticide, alcohol drinking, history of depression were 55.2%, 34.0%, 41.4% and the RERIs were 8.96, 3.31, 7.85 respectively. The heritability of PD patients' first degree relatives was 36.86% +/- 5.76%, and second degree relatives was 20.66% +/- 6.81%. CONCLUSION: Family history of PD had an additive model synergism on PD, coexisting with other risk factors. Genetic factors had a smaller action on PD than environmental factors.