Gene and gene expression

Gene and gene expression

The information necessary to produce proteins in cells is encoded in the genetic material—the chromosomal strands, which are made of deoxyribo-nucleic acid (DNA). A gene is a sequence of the chromosome that codes for a specific protein. Thus, genes are made of DNA and contain information to produce specific proteins.

Transcription is a nuclear process whereby information from DNA is transferred to messenger ribonucleic acid (mRNA). In this process, the two complementary strands of the DNA partly uncoil. The sense strand sepa-rates from the antisense strand. The antisense strand of DNA is used as a template by the transcribing enzymes to assemble complementarity-defined mRNA. Then, mRNA migrates into the cytoplasm, where ribosomes transfer the encoded information in mRNA’s base sequence in a comple-mentarity-defined manner to assemble proteins. This process is called translation. The long strings of amino acids (called polypeptide chains) thus generated can fold by themselves or assemble with other polypeptide chains to form a specific protein. The covalently linked amino acids constitute the primary structure of proteins. These folding and assembly processes hap-pen through multiple noncovalent (such as hydrophobic, hydrogen bond, and ionic) interactions, leading to the secondary, tertiary, and quaternary structure of proteins. Some proteins additionally undergo posttranslational modifications, such as the attachment of a glycan (carbohydrate) moiety to the protein by a cytoplasmic enzyme. The assembled, functional proteins then migrate to their site of action—which can be membrane, cytoplasmic, intraorgnelle (such as intranuclear or intramitochondrial), or extracellular (secreted proteins, such as hormones).