Quantitative Trait Loci
QTLs are identified through genetic linkage analysis, allowing researchers to pinpoint genomic locations associated with specific phenotypes.
Locating and studying QTLs is crucial for understanding the genetic basis of complex traits and developing targeted interventions.
PubCompare.ai's AI-driven platform streamlines the QTL research process, helping scientists easily identify and compare protocols from literature, preprints, and patents to enhance reproducibility and optimize experimental design.
This cutting-edg AI technology takes the guesswork out of protocol selection, empowering researchers to make informed decisions and drive their QTL studies forward with confidence.
Most cited protocols related to «Quantitative Trait Loci»
Initialization. We determine a nominal P value threshold of significance on a per-phenotype basis. To do so, we first perform a permutation pass as described above which gives us an adjusted P value per phenotype (or group of phenotypes) together with its most likely beta parameter values. Next, we determine the adjusted P value threshold corresponding to the targeted FDR level (for example, 5% FDR) and feed the beta quantile function (for example, R/q beta) with it to get a specific nominal P value threshold for each phenotype. Here, the beta quantile function allows us to use the Beta distribution in a reversed way: from adjusted P value to nominal P value. Note that the resulting nominal P value thresholds vary from one phenotype to the other depending on the complexity of the cis regions being tested and the effective number of independent tests they encapsulate.
Forward pass. We next learn the number of independent signals per phenotype using stepwise regressions with forward variable selection. More specifically, we start from the original phenotype quantifications and search for the variant in cis with the strongest association. When the corresponding nominal P value of association is below the threshold defined in step (1), we store the variant as additional and independent discovery and residualize its genotypes out from the phenotype quantifications. We then repeat these two steps until no more significant discovery is made: this immediately gives us the number of independent molQTLs together with a best candidate variant for each.
Backward pass. Finally, we try to assign nearby genetic variants to the various independent signals we discovered in step (2). To do so, we define a linear regression model that contains all candidate QTLs discovered so far in the forward pass: P=Q1+…+Qi+…+QR where R is the number of independent signals and {Q1, …, Qi, …, QR} are the corresponding best molQTL candidates. Then, we test all possible hypotheses by fitting this model Rx(L-R) times each time fixing { Q1, …, Qi−1, Qi+1,…, QR } and setting Qi as another variant in cis (L–R variants in cis not being a candidate molQTL times R independent signals). We then end up with a vector of R nominal P values for each variant in cis which allows us to determine the signal the variant belongs to by simply finding the smallest P value in this vector and comparing it to the significance threshold obtained in step (1).
Using data from previously published studies of whole-genome gene expression and genome-wide genotyping,25–29 we assessed whether variants at associated loci (identified as described in the Statistical analysis) regulate levels of mRNA. These expression quantitative trait loci (eQTL) studies included non-tumour lung tissue, blood, and, for variants associated with smoking behaviour, brain. For genes close to peaks of novel signals or genes implicated through eQTL, we assessed differential expression in the lungs of individuals with and without COPD and differential expression in the pseudoglandular and canalicular stages of development of the fetal lung.30,31 Additionally, we generated RNA sequencing data to discover novel transcripts of these genes in human bronchial epithelial cells. We tested all genome-wide meta-analysis p values for enrichment in biological pathways defined in publicly available databases. All functional analyses are described in detail in the
Most recents protocols related to «Quantitative Trait Loci»
The polymorphic SSR markers were used to construct a schematic map illustrating the genomic contributions of donor and recurrent parents with Graphical GenoType (GGT) v2.045 software to identify backcross-derived lines possessing the maximum recurrent parent genome. The positive foreground-selected plants genotyped for polymorphic markers at each backcross/selfing generation and recurrent parent genome recovery (G) were estimated using the following formula: G = [(X + ½Y) × 100]/N; here, N is the total number of parental polymorphic markers screened, X is the number of markers showing homozygosity for recurrent parental alleles, and Y is the number of markers showing heterozygosity for parental alleles. Based on the recovery of the recurrent parental genome and the presence of targeted donor genomic regions, 50 lines were selected from BC2F1 and BC1F2 plants and advanced through selfing.
Thirteen plants were selected from advanced BC2F2 lines based on maximum recovery for RPG through background and foreground selection and visible phenotypic similarity with the recurrent parent strain, HD2733, while BC1F3 lines were selfed and advanced to BC1F4 generations. A total of 10 BC1F4 plants were again selected based on foreground selection and maximum background recovery of the recurrent parental genome. The selected 13 BC2F3 and 10 BC1F4 plants were evaluated for morphological and physiological traits and yield performance and further advanced through selfing for evaluation under a national testing trial.
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More about "Quantitative Trait Loci"
QTLs are identified through genetic linkage analysis, allowing researchers to pinpoint genomic locations associated with specific phenotypes.
Locating and studying QTLs is crucial for understanding the genetic basis of complex traits and developing targeted interventions.
PubCompare.ai's AI-driven platform streamlines the QTL research process, helping scientists easily identify and compare protocols from literature, preprints, and patents to enhance reproducibility and optimize experimental design.
This cutting-edge AI technology takes the guesswork out of protocol selection, empowering researchers to make informed decisions and drive their QTL studies forward with confidence.
The process of QTL identification often involves the use of statistical software like SAS 9.4, which can be used to perform linkage analysis and identify regions of the genome associated with quantitative traits.
Additionally, genotyping technologies such as the GoldenGate assay and the Infinium assay, as well as the NanoDrop 1000 spectrophotometer and the MassARRAY iPLEX platform, can be used to generate and analyze genetic data for QTL studies.
Other software tools like SPSS Statistics 19 and GenomeStudio, a suite of analysis tools for microarray data, can also be utilized in the QTL research process.
The GenomeStudio software, particularly the version 2011.1, has been widely used in QTL studies to visualize and analyze genetic data.
Overall, the combination of advanced statistical analysis, high-throughput genotyping technologies, and intuitive data visualization tools has been instrumental in the advancement of QTL research, enabling researchers to uncover the genetic underpinnings of complex traits and develop more effective interventions.