Elongaation

Elongaation, more commonly spelled elongation, is the process of lengthening or extending something. In biology, the term is used for several distinct, but related, processes in which a dimension increases rather than merely growing in number of units. The word derives from Latin elongare, to lengthen.

In developmental biology, elongation often refers to tissue or cellular lengthening. Plant cells elongate by loosening and expanding their cell walls under turgor pressure, a process influenced by hormones such as auxin. In bacteria and some fungi, cells can elongate during growth or before division, producing elongated, rod-shaped forms.

In molecular biology, transcription elongation describes the stage after initiation in which RNA polymerase traverses the DNA template to synthesize RNA. The enzyme adds nucleotides in a 5' to 3' direction, with pausing and backtracking regulated by elongation factors. Rates vary by organism, on the order of tens of nucleotides per second in bacteria and several kilobases per minute in eukaryotes. Termination follows elongation as signals or processing cues are encountered.

During translation elongation, the ribosome moves along an mRNA, decoding codons and forming peptide bonds between amino acids carried by tRNAs. This process uses elongation factors (such as EF-Tu/EF-G in bacteria or eEF1A/eEF2 in eukaryotes) and consumes GTP. Typical rates are a few to several amino acids added per second, depending on organism and cellular conditions.

Elongation is tightly regulated and essential to proper gene expression, growth, and development. Disruptions to elongation can affect development, stress responses, or disease states.