Intramuscular fat content, also assessed as marbling of meat, represents an important beef quality trait. Recent work has mapped a quantitative trait locus (QTL) with an effect on marbling to the centromeric region of bovine chromosome 14, with the gene encoding thyroglobulin (TG) being proposed as a positional and functional candidate gene for this QTL. Recently, the gene encoding diacylglycerol O-acyltransferase (DGAT1), which also has been mapped within the region of the marbling QTL, has been demonstrated to affect the fat content of milk. In the present study, the effects of a 5'-polymorphism of TG and of a lysine/alanine polymorphism of DGAT1 on the fat content of musculus (m.) semitendinosus and m. longissimus dorsi in 55 bovine animals (28 German Holstein and 27 Charolais) has been investigated. Significant effects were found for both candidate genes in both the breeds. These effects seem to be independent of one another because the alleles of the two polymorphisms showed no statistically significant disequilibrium. The DGAT1 effect is mainly on the m. semitendinosus. The TG polymorphism only affects m. longissimus dorsi. However, both intramuscular fat enhancing effects seem to be recessive. The possibility of two linked loci, acting recessively on intramuscular fat content, will require special strategies when selecting for higher marbling scores.

Haplotypes derived from five polymorphic restriction sites in the beta-globin gene cluster were investigated in 139 individuals from five different Brazilian Indian tribes by the polymerase chain reaction (PCR). Eight haplotypes were identified. Haplotypes 2 ((+)----) and 6 (-)++(-)+) were the most frequent and were common to all tribes. Their prevalences ranged from 60% to 93% and from 3% to 18%, respectively. Average heterozygosity measured by the Gini-Simpson index is markedly reduced among these Brazilian Indians when compared with Europeans (56%), but much less (8%) in relation to Asiatics, suggesting the absence of an important bottleneck effect in the early colonization of South America. The coefficient of gene differentiation (GST') was estimated as 0.082 among six Brazilian Indian tribes, but when only three Tupi-Mondé-speaking tribes were considered, this estimate was reduced to 0.030.

Lipoprotein lipase is the rate-limiting enzyme in the lipolysis of plasma triglyceride-rich lipoproteins. We studied six variants (T-93G, D9N, N291S, PvuII, HindIII and S447X) in the lipoprotein lipase (LPL) gene in 309 non-diabetic patients with angiographically assessed coronary artery disease and in 197 controls in a southern Brazilian population of European descent. The HindIII H-allele was associated with lower triglycerides (p < 0.01) and higher high-density lipoprotein cholesterol (p = 0.03) levels, and the S447X mutation was associated with lower triglyceride levels (p < 0.01) in males, but not females. No other significant lipid associations were observed. Haplotypes were derived from these two sites (HindIII/S447X), and carriers of H-S and H-X haplotypes showed lower triglycerides (p < 0.01) and increased high-density lipoprotein cholesterol (p = 0.01) levels when compared to the H+S haplotype in males. In this gender, the H-X haplotype was associated with a protective effect (OR = 0.36, 95%CI = 0.13-0.97) for significant disease (> or = 60% of luminal coronary stenosis), even controlling for other classical risk factors.

We developed two multiplex systems for the coamplification of X-chromosomal short tandem repeats (STRs). X-Multiplex 1 consisted of DXS6807, DXS6800, DXS7424, DXS101, GATA172D05 and HPRTB and X-Multiplex 2 consisted of DXS8378, DXS9898, DXS6801, DXS6809, DXS6789, DXS7133, DXS8377 and DXS7423. In addition, we present allele frequencies for these loci in a south Brazilian population comprising 124 females and 141 males and haplotype frequencies of linked markers for males. Hardy-Weinberg equilibrium (HWE) was tested in the female sample and no significant deviations were found after applying Bonferroni's correction. Linkage disequilibrium (LD) tests were performed for all pairs of loci and three significant results, out of 91 pairwise comparisons, were obtained. We did not find any evidence of linkage disequilibrium between close or linked markers. The power of discrimination in females (PD(F)) varied between 0.832 for DXS6801 and 0.987 for DXS8377. DXS6801 was the least informative marker (PIC = 0.605), while DXS8377 was the most polymorphic (PIC = 0.911), followed by DXS101 (PIC = 0.872). Genetic distances were estimated for each STR marker applying the calculation of F (ST) between our total sample and other studies from Brazil, Europe, Asia and Africa. The most distant populations were Japan, Korea, China, Ghana and Uganda.

Allele and haplotype frequencies for the T-93G, Hind III, and Pvu II variants of the lipoprotein lipase gene (LPL), and Hpa I and Ava II restriction site polymorphisms (RSP) of the APOE/C-I/C-II gene cluster were determined in 143 individuals from five Brazilian Indian tribes. These results were integrated with those previously reported for APOE. Marked interethnic variability occurs in these sites. A strong linkage disequilibrium was observed between the APOE and APOC-I loci (D' = 0.81; P < 0.00001). Linkage disequilibrium between the Hind III and Pvu II RSPs of the LPL gene was also observed (D' = 1; P < 0.001), but none of these RSPs were in linkage disequilibrium with the T-93G mutation. Considering both loci, heterozygosity was estimated as 0.45, but it was lower in the Xavante and Surui populations, in accordance with the historical and biodemographical data of these Amerindians. The results reported here may have implications for understanding interpopulation differences in lipid levels and coronary heart disease prevalences.