Sequential and contingent changes in gene expression strongly influence the development of organisms and responses to the environment. These dynamic biological programs are executed via complex and still poorly defined networks of interactions among genes, transcripts, proteins and numerous small molecules and cofactors. A new strategy called as “genetical genomics’, will allow geneticists to take more advantage of genomics. The strategy uses the genetic variation between related individuals in a segregating population and adds the analytical tools available for molecular markers to the analysis of genome-wide expression profile data. In principle, genetical genomics can generate substantial additional insight into the function and interrelation of gene products and gene action from any method of expression profiling based on RNA, protein or metabolites¹.

The serendipitous overlap between regulatory and disease-associated variants can be expected to increase with the higher resolution and higher discovery rates of RNA-seqbased eQTL studies. Expression quantitative trait locus (eQTL) mapping is a method used to determine the effects of genetic variants on gene expression levels. Recent RNA-sequencing (RNA-seq) studies have shown that a large repertoire of transcripts is available in cells, which are actively regulated by (trait-associated) variants. cDNA and oligonucleotide microarray technologies hold great promise for identifying candidate genes and for monitoring the expression of mRNAs or the occurrence of polymorphisms in genomic DNA².

A study was carried out to identify more than 2000 genetic polymorphisms (transcript derived markers, TDMs) from an experiment involving two commercial varieties of barley (Hordeum vulgare; Steptoe and Morex) with this set of TDM a genetic map was constructed and later it was used for the genome-wide eQTL analysis of about 16 000 genes3. The added value of genetical genomics should stimulate the development of appropriate and cost-effective analytical and statistical technologies: the merger of genomics and genetics will indeed combine the better of two worlds.

References: 

1. JANSEN, R. C. AND NAP, J. P., 2001, Genetical genomics: the added value from segregation. TRENDS in Genetics, 17(7): 388-391. 

2. PFLIEGER, S., LEFEBVRE, V. AND CAUSSE, M., 2001, The candidate gene approach in plant genetics: a review. Mol. breeding, 7(4), 275-291.

 3. POTOKINA, E., DRUKA, A., LUO, Z., WISE, R., WAUGH, R. AND KEARSEY, M., 2008, Gene expression quantitative trait locus analysis of 16,000 barley genes reveals a complex pattern of genome‐wide transcriptional regulation. The Plant J., 53(1), 90-101.