Start codon

Definition

A start codon is a specific sequence of nucleotides in mRNA that signals the beginning of translation. It typically codes for the amino acid methionine in eukaryotes and formyl-methionine in prokaryotes.

5 Must Know Facts For Your Next Test

1. The most common start codon is AUG.
2. It is essential for proper initiation of protein synthesis.
3. Mutations affecting the start codon can lead to severe disruptions in protein production.
4. In some rare cases, alternative start codons like GUG or UUG can be used in prokaryotes.
5. The start codon establishes the reading frame for the ribosome during translation.

Review Questions

• What nucleotide sequence is most commonly known as the start codon?
• Why is the start codon crucial for protein synthesis?
• Can alternative start codons exist and, if so, in which type of organisms are they found?

Related terms

mRNA: Messenger RNA that carries genetic information from DNA to the ribosome.

Ribosome: Cellular machinery where proteins are synthesized.

Translation: The process by which a ribosome decodes mRNA into a polypeptide chain.