Elongation is the process during transcription and translation where a growing chain of RNA or polypeptide is extended. In transcription, elongation refers to the synthesis of RNA from a DNA template, while in translation, it describes the addition of amino acids to a polypeptide chain as directed by mRNA. Both processes are crucial for gene expression and involve the sequential addition of nucleotides or amino acids.
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During transcription elongation, RNA polymerase moves along the DNA template strand, unwinding the double helix and adding ribonucleotides to the growing RNA chain in a 5' to 3' direction.
In translation elongation, aminoacyl-tRNA molecules bring specific amino acids to the ribosome, matching their anticodon with codons on the mRNA.
The elongation phase in both transcription and translation is crucial for accurate and efficient gene expression, affecting the final protein product.
Elongation factors are proteins that assist in the elongation phase of translation by facilitating the entry of tRNA into the ribosome and ensuring proper peptide bond formation.
Termination signals are key for concluding elongation, as they dictate when RNA synthesis or polypeptide assembly should stop, ensuring the correct length and functionality of the resulting molecules.
Review Questions
How does the elongation process differ between transcription and translation?
Elongation in transcription involves RNA polymerase synthesizing RNA from a DNA template, adding ribonucleotides one by one to form a growing RNA strand. In contrast, elongation in translation involves ribosomes facilitating the addition of amino acids brought by tRNA to a growing polypeptide chain based on the sequence of codons in mRNA. While both processes extend a chain, they differ in their substrates (nucleotides versus amino acids) and machinery (RNA polymerase versus ribosomes).
What roles do elongation factors play in translation, and why are they important?
Elongation factors are critical proteins that assist in the translation elongation process by promoting the correct entry of aminoacyl-tRNA into the ribosome and ensuring that peptide bonds are formed efficiently between amino acids. These factors help maintain the accuracy and speed of protein synthesis, allowing cells to produce proteins effectively. If elongation factors malfunction or are absent, it can lead to errors in protein synthesis, potentially disrupting cellular functions.
Evaluate how disruptions in the elongation phase can affect gene expression and overall cellular function.
Disruptions during elongation can significantly impair gene expression by either halting RNA synthesis or producing incomplete or dysfunctional proteins. If transcription elongation is affected, insufficient mRNA may be produced, leading to inadequate protein levels necessary for vital cellular processes. Similarly, if translation elongation is disrupted, it can result in truncated proteins that may lack essential functional domains. Such disruptions can lead to various cellular dysfunctions and diseases, highlighting the importance of properly regulated elongation phases.