Regulating Genetic Expression and Evolution

Gene Expression Map of Human Body Gives Value to Variants

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Gene expression is a technique through which genetic instruction are used for synthesizing gene products. This technique enables scientists and researchers to reach at the molecular level of each gene. Proteins are generally synthesized with the help of gene expression which further perform the function of components such as proteins, enzymes as well as receptors. Process of gene expression involves of two stages, transcription and translation. The techniques used for monitoring the gene expression levels include, northern blot analysis, RNA protection assay, and microarrays among others.

Most genetic variations between people have little or no effect on health. The variants that have been linked to human health conditions often alter how genes are expressed-when and where they’re turned on and off. Scientists have only just begun to understand how these variations in different tissues of the body affect human biology and disease.

The DNA packaged neatly inside the nucleus of almost every cell in a person may be identical, but which parts are translated varies dramatically by cell type and by individual genome. In a Herculean effort to connect form to function, the Genotype-Tissue Expression (GTEx) project correlated genetic variations in 449 people with gene expression patterns among 44 postmortem tissue samples, including 10 regions in the brain. Published in four papers in the October 11 Nature, the data present a bird’s-eye view of the diversity of gene regulation across the human body and across the human population. While some genetic variations exerted similar sway over gene expression in most organs, others modulated transcription in specific tissues. The landscape of gene regulation in the brain emerged as strikingly distinctive from other regions of the body.

Transcription

The production of a RNA copy from a DNA strand is called transcription, and is performed by RNA polymerases, which add one ribonucleotide at a time to a growing RNA strand as per the complementarity law of the nucleotide bases. This RNA is complementary to the template 3' → 5' DNA strand, with the exception that thymines (T) are replaced with uracils (U) in the RNA.

mRNA processing

While transcription of prokaryotic protein-coding genes creates messenger RNA (mRNA) that is ready for translation into protein, transcription of eukaryotic genes leaves a primary transcript of RNA (pre-RNA), which first has to undergo a series of modifications to become a mature RNA. Types and steps involved in the maturation processes vary between coding and non-coding preRNAs; i.e. even though preRNA molecules for both mRNA and tRNA undergo splicing, the steps and machinery involved are different. The processing of non-coding RNA is described below (non-coring RNA maturation).

The processing of premRNA include 5' capping, which is set of enzymatic reactions that add 7-methylguanosine (m7G) to the 5' end of pre-mRNA and thus protect the RNA from degradation by exonucleases. The m7G cap is then bound by cap binding complex heterodimer (CBC20/CBC80), which aids in mRNA export to cytoplasm and also protect the RNA from decapping.

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