Genomic deoxyribonucleic acid is chromosomal DNA, in contrast to extrachromosomal DNAs like plasmids. It is often abbreviated as gDNA. Most organisms contain the same genomic DNA in every cell; however, only certain genes are active in each cell to allow for cell function and differentiation within the body.
The genome of an organism (encoded by the genomic DNA) is the biological information of heredity which is passed from one generation of organism to the next. That genome is transcribed to produce various RNAs, which are necessary for the function of the organism. Precursor mRNA (pre-mRNA) is transcribed by RNA polymerase II in the nucleus. pre-mRNA is then processed by splicing to remove introns, leaving the exons in the mature messenger RNA (mRNA). Additional processing includes the addition of a 5' cap and a poly(A) tail to the pre-mRNA. The mature mRNA may then be transported to the cytosol and translated by the ribosome into a protein. Other types of RNA include ribosomal RNA (rRNA) and transfer RNA (tRNA). These types are both transcribed by RNA polymerase III and are essential for protein synthesis.
Genomic DNA uses the standard genetic code for protein synthesis. This universal code is used to match specific tRNAs carrying amino acids to their respective three-nucleotide codons found within the exons of genomic DNA (see Protein biosynthesis).
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