Codon

Definition

A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid during protein synthesis. These triplets are crucial in determining the genetic code, which guides the assembly of amino acids into proteins, ultimately impacting gene expression and regulation. Codons are the bridge between the nucleotide sequence of DNA and the corresponding protein products, making them essential for translation and understanding the genetic code.

5 Must Know Facts For Your Next Test

1. There are 64 possible codons, with 61 coding for amino acids and 3 serving as stop signals.
2. Codons are read in a non-overlapping manner during translation, meaning each nucleotide is part of only one codon.
3. The genetic code is nearly universal, allowing for the same codons to code for the same amino acids across diverse organisms.
4. Start codons, such as AUG, not only signal the beginning of translation but also code for the amino acid methionine.
5. Mutations in codons can lead to changes in amino acid sequences, potentially resulting in nonfunctional proteins or diseases.

Review Questions

• How do codons function in the process of translation and what role do they play in gene expression?
  • Codons function as instructions during translation by specifying which amino acids should be added to the growing polypeptide chain. Each codon corresponds to a specific amino acid or a stop signal, ensuring that the correct sequence is formed according to the genetic information encoded in mRNA. This process directly influences gene expression, as the protein produced can determine cellular functions and traits.
• What implications does the redundancy of the genetic code have for mutations affecting codons?
  • The redundancy of the genetic code means that multiple codons can encode for the same amino acid, which can mitigate the effects of mutations. For example, if a mutation changes one nucleotide in a codon, it may still result in the same amino acid being incorporated due to this redundancy. However, some mutations can lead to changes in amino acids or introduce stop codons, potentially disrupting protein function and leading to various genetic disorders.
• Evaluate the significance of start and stop codons in protein synthesis and how they contribute to cellular functions.
  • Start and stop codons are vital for proper protein synthesis; they mark where translation begins and ends. The start codon (typically AUG) not only initiates translation but also codes for methionine, an essential amino acid for protein formation. Stop codons signal termination, ensuring that proteins are synthesized to their correct length. Any errors with these codons can lead to incomplete or dysfunctional proteins, impacting cellular functions and potentially resulting in diseases.

Related terms

anticodon: A sequence of three nucleotides in tRNA that pairs with the complementary codon in mRNA during translation.

genetic code: The set of rules by which information encoded in genetic material is translated into proteins, consisting of 64 codons that correspond to 20 amino acids.

stop codon: A specific codon that signals the termination of protein synthesis, indicating that the polypeptide chain is complete.