So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Evolution of Protein Molecules

Heritability (H) on a progeny mean basis is frequently estimated in recurrent selection experiments for the purpose of estimating the expected progress from family selection; however, appropriate measures of precision have been developed for only a few heritability estimators. The objective of this research was to develop a measure of precision for H for certain balanced linear models. Exact confidence intervals for H were derived and are not restricted to a specific experimental design. The confidence intervals were applied to sorghum [Sorghum bicolor (L.) Moench] half-sib family data.

An exact confidence interval for heritability on a progeny mean basis

/pdf/food-and-agricultural-organization-of-the-united-nations-151qubr5t3.pdf

Food and Agricultural Organization of the United Nations.

Maize kernel oil is a valuable source of nutrition. Here we extensively examine the genetic architecture of maize oil biosynthesis in a genome-wide association study using 1.03 million SNPs characterized in 368 maize inbred lines, including ‘high-oil’ lines. We identified 74 loci significantly associated with kernel oil concentration and fatty acid composition (P < 1.8 × 10 −6 ), which we subsequently examined using expression quantitative trait loci (QTL) mapping, linkage mapping and coexpression analysis. More than half of the identified loci localized in mapped QTL intervals, and one-third of the candidate genes were annotated as enzymes in the oil metabolic pathway. The 26 loci associated with oil concentration could explain up to 83% of the phenotypic variation using a simple additive model. Our results provide insights into the genetic basis of oil biosynthesis in maize kernels and may facilitate marker-based breeding for oil quantity and quality.

/pdf/genome-wide-association-study-dissects-the-genetic-1g1h5gsuq7.pdf

Genome-wide association study dissects the genetic architecture of oil biosynthesis in maize kernels

Maize cultivars often have low kernel oil content. To increase the oil content, efficient maize breeding programs have to be developed, which require the knowledge of the inheritance of this trait. Thus, the objective of this research was to map quantitative trait locus (QTLs) and estimate their effects for kernel oil content in a tropical maize population. Two maize inbred lines, contrasting for kernel oil content, were used to develop an F2 population. Four hundred and eight F2 plants were self-pollinated, and their kernels (F2:3 progenies) were used for kernel oil evaluation. A genetic map with 75 microsatellites was developed, and the QTLs were mapped using the composite interval map (CIM); also, estimates of genetic and phenotypic variances, and heritability coefficient were computed. The map presented 10 linkage groups, spanned 1,438.6 cM in length with an average interval of 19.18 cM between adjacent markers. The kernel oil content averaged 58.40 g kg−1, and the broad-sense heritability was high (h2= 0.98). Thirteen QTLs were mapped, which were distributed into eight chromosomes, and explained 26.64% of the genetic variation. QTLs in chromosomes 1, 5, and 6 contributed the most for kernel oil content. Nine out of 13 QTLs with favorable alleles were from the parental inbred with the highest kernel oil content. The average level of dominance was partial, but gene action of the QTLs ranged from additive to overdominance. Eight out of 13 mapped QTLs were already reported for temperate maize populations.

Mapping QTLs for kernel oil content in a tropical maize population.

We have studied the beta spectrum of {sup 14}C using a unique {sup 14}C-doped germanium detector. In 1991 an initial report was made of a distortion in the spectrum that could be explained by the emission of a 17-keV neutrino in approximately 1% of the decays. Further tests have shown that the observed distortion was most likely caused by systematic effects related to the detector`s active guard ring. A new measurement with a smaller data sample shows no sign of this distortion. In addition, we find the {ital Q} value of {sup 14}C decay to be 155.95{plus_minus}0.07(stat.){plus_minus}0.21(sys.) keV, in disagreement with a previous precision measurement.

/pdf/further-studies-on-the-evidence-for-a-17-kev-neutrino-in-a-47pyzvx5fh.pdf

Further studies on the evidence for a 17-keV neutrino in a {sup 14}C-doped germanium detector

Sugarcane (Saccharum spp.) is highly polyploid and aneuploid. Modern cultivars are derived from hybridization between S. officinarum (x = 10, 2n = 80) and S. spontaneum (x = 8, 2n = 40−128). The hypothetical HP600 and centromere protein C (CENP−C) genes from sugarcane were used to elucidate the allelic expression and genomic and genetic behavior of this complex polyploid. The genomically side−by−side genes HP600 and CENP-C were found in two different homeologous chromosome groups with ploidies of eight and ten. The first region (Region01) was a Sorghum bicolor ortholog with all haplotypes of HP600 and CENP-C expressed, but HP600 exhibited an unbalanced haplotype expression. The second region (Region02) was a scrambled sugarcane sequence formed from different noncollinear genes containing duplications of HP600 and CENP-C (paralogs). This duplication occurred before the Saccharum genus formation and after the separation of sorghum and sugarcane, resulting in a nonexpressed HP600 pseudogene and a recombined fusion version of CENP−C and orthologous gene Sobic.003G299500 with at least two chimerical gene haplotypes expressed. The genetic map construction supported the difficulty of mapping markers located in duplicated regions of complex polyploid genomes. We thus present an integrated approach to elucidate the homeolog dynamics of polyploid genomes.

/pdf/genetic-variation-in-a-complex-polyploid-unveiling-the-4byd8mpked.pdf

Genetic variation in a complex polyploid: unveiling the dynamic allelic features of sugarcane

We have performed a search for the [beta][sup +] decay of [sup 54]Mn by looking for back-to-back 511-keV [gamma] rays in two high-purity Ge detectors. No excess of events above background was observed, and a limit of 5.7[times]10[sup [minus]7]% has been established for the [beta][sup +] branch. The significance of this result for the use of [sup 54]Mn as a cosmic ray chronometer is discussed.

/pdf/search-for-the-beta-decay-of-54mn-4woofjghuc.pdf

A. Garcia

Papers

Mapping QTLs for kernel oil content in a tropical maize population.

Further studies on the evidence for a 17-keV neutrino in a {sup 14}C-doped germanium detector

Genetic variation in a complex polyploid: unveiling the dynamic allelic features of sugarcane

Search for the beta + decay of 54Mn.

β-Decay and Cosmic-Ray Half-Life of 54 Mn