A strategy of DNA pooling aimed at identifying markers linked to quantitative trait loci (QTLs), 'Sequential Bulked Typing' (SBT), is presented. The method proposed consists in pooling DNA from consecutive pairs of individuals ranked phenotypically, i.e., pools are formed with individuals ranked (1st, 2nd), (3rd, 4th),…, (N-1st, Nth). The N/2 pools are subsequently amplified using the polymerase chain reaction (PCR). If the whole population is typed the number of PCRs per marker is halved with respect to individual typing (IT). But if this strategy is combined with selective genotyping of extreme individuals savings can be further increased. Two extreme cases are considered: in the first one (SBT(0)), it is assumed that only presence or absence of a given allele can be ascertained in a pool; in the second one (SBT(1)), it is further assumed that differences between allele band intensities can be distinguished. The theory to estimate by maximum likelihood the QTL effect and its position with respect to flanking markers is presented. The behaviour of IT and SBT was studied using stochastic computer simulation in backcross and F2 populations. Three percentages of subpattern distinction (0, 50 and 100%) two population sizes (n=1200 and 600) and two QTL effects (a=0.1 and 0.25 standard deviations) were considered. SBT(1) had the same power as individual genotyping at half the genotyping costs in all situations studied. Accuracy of QTL location is not increased with a dense number of markers, as opposed to individual typing. As a result DNA pooling is not useful for accurate location of the QTL but rather to pick up genome regions containing QTLs of at least moderate effect. The theory developed provides the general theoretical framework to deal with any DNA pooling strategy aimed at detecting QTLs.

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Objective:Vitamin D receptor (VDR) gene polymorphism have a role in diabetes mellitus pathogenesis. Present study was conducted to determine VDR gene variants among Saudi gestational diabetics (GDM) in Madina, KSA.Methods:This cross sectional study was conducted on 112 GDM patients and 218 normal healthy control. Age, body mass index and blood pressure levels were recorded. Serum triglycerides (mg/dl), total cholesterol, HDL-cholesterol, LDL-cholesterol, fasting blood glucose FBG and post-prandial blood glucose PPBG were estimated. Extracted DNA template was amplified by PCR reaction and genotyped for single nucleotide polymorphism of BsmI and FokI by restriction fragment length polymorphism-PCR (RFLP-PCR) analysis.Results:FBG and PPBG levels in GDM patients were significantly elevated by +48.6% and +50%, respectively (P=0.005). Serum triglycerides, total cholesterol and LDL-cholesterol (mg/dl) levels in GDM patients were elevated significantly by +40.5% (P=0.005), +16% (P=0.01) and +30.8% (P=0.005), respectively. Serum HDL-cholesterol (mg/dl) showed significant decline by -10.5%. FokI VDR genotypes showed association with PPBG (P=0.05) among GDM patients. The Ff, FF and ff genotype percentage among GDM patients was 48.2%, 30.4% and 21.4%, respectively. FokI (F and f) and BsmI (B and b) alleles frequency showed no significant difference between GDM patients and control. Percentage BsmI and FokI total homozygous and heterozygous variants among GDM was 45.5% and 81.4%, respectively.Conclusion:VDR BsmI and FokI polymorphic marker not associated with Saudi GDM.

Toll-like receptor 4 (TLR4) plays an important role in modulating innate immunity. Type 2 diabetes mellitus (T2DM) is a chronic disease that is characterized by impaired insulin resistance and abnormal immune response. Genetic background and consequently genetic factors might have a key role in both onset and progression of T2DM-related complications. The aim of this work was to study the role of toll-like receptor 4 (TLR4) in the development of type 2 diabetes mellitus (T2DM). This study was carried out on 90 subjects, 30 type 2 diabetic patients, 30 patients with impaired glucose tolerance and 30 age and gender matched healthy controls. mRNA expression of (TLR4) was assessed by reverse transcriptase PCR (RT-PCR) using real time PCR.. Results showed significant statistical difference between the three studied groups regarding BMI, serum FBG, HDL, TGs, TC, LDL, HOMA -IR and mRNA expression of TLR4 with highest level of TLR4 mRNA expression in T2DM patients. From this study, it might be concluded that high expression of (TLR4) is associated with T2DM.

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