Elongation

Definition

Elongation is the process of extending or lengthening a molecule or structure. In the context of molecular biology, it refers to the continuous addition of subunits to a growing polymer, such as DNA, RNA, or a polypeptide chain, during the processes of replication, transcription, and translation, respectively.

5 Must Know Facts For Your Next Test

1. During DNA replication, the elongation phase involves the continuous addition of nucleotides to the growing DNA strands by the DNA polymerase enzyme.
2. In RNA transcription, elongation refers to the continuous addition of ribonucleotides to the growing RNA transcript by the RNA polymerase enzyme.
3. During protein synthesis (translation), the elongation phase involves the continuous addition of amino acids to the growing polypeptide chain by the ribosome.
4. Processivity is an important feature of elongation, as it allows enzymes like DNA polymerase and RNA polymerase to remain bound to their templates and efficiently catalyze multiple rounds of synthesis.
5. The rate of elongation can be influenced by various factors, such as the availability of precursor molecules, the activity of regulatory enzymes, and the presence of pausing or termination signals.

Review Questions

• Explain the role of elongation in the process of DNA replication.
  • During DNA replication, the elongation phase involves the continuous addition of nucleotides to the growing DNA strands by the DNA polymerase enzyme. This process occurs on both the leading and lagging strands, with DNA polymerase III adding nucleotides to the 3' end of the growing DNA molecule. Elongation is a crucial step in ensuring the accurate and complete duplication of the entire genome, as it allows for the continuous synthesis of new DNA molecules from the original template.
• Describe how elongation contributes to the process of RNA transcription.
  • In the process of RNA transcription, the elongation phase refers to the continuous addition of ribonucleotides to the growing RNA transcript by the RNA polymerase enzyme. As RNA polymerase moves along the DNA template, it catalyzes the incorporation of ribonucleotides to the 3' end of the nascent RNA molecule. This elongation step is essential for the production of a complete and functional RNA transcript, which can then be used for various cellular processes, such as protein synthesis or gene regulation.
• Analyze the importance of elongation in the context of protein synthesis (translation).
  • During protein synthesis, the elongation phase involves the continuous addition of amino acids to the growing polypeptide chain by the ribosome. As the ribosome moves along the mRNA template, it catalyzes the incorporation of specific amino acids, as dictated by the codon sequence, to the C-terminus of the polypeptide. This elongation process is crucial for the synthesis of a complete and functional protein, as it ensures the accurate and efficient translation of the genetic information encoded in the mRNA. The processivity of the ribosome during elongation is a key factor in maintaining the fidelity of protein synthesis.

Related terms

Initiation:

The starting point of a biological process, such as the beginning of DNA replication, RNA transcription, or protein synthesis.

Termination:

The end of a biological process, such as the completion of DNA replication, RNA transcription, or protein synthesis.

Processivity: The ability of an enzyme to catalyze multiple rounds of a reaction without dissociating from the substrate.