Codon

Definition

A codon is a sequence of three nucleotides in DNA or RNA that corresponds to a specific amino acid or a stop signal during protein synthesis. Codons play a crucial role in the process of translation, where the genetic code is converted into a functional protein. Each codon is essential for ensuring the correct sequence of amino acids, which ultimately determines the structure and function of the resulting protein.

5 Must Know Facts For Your Next Test

1. There are 64 possible codons, consisting of 61 codons that specify amino acids and 3 stop codons that signal the termination of protein synthesis.
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, meaning that most organisms use the same codons to encode the same amino acids, showcasing the commonality of life.
4. Mutations in codons can lead to changes in the amino acid sequence of proteins, which can affect protein function and lead to various diseases.
5. The start codon, AUG, not only signals the beginning of protein synthesis but also codes for the amino acid methionine.

Review Questions

• How do codons contribute to the accuracy of protein synthesis?
  • Codons contribute to the accuracy of protein synthesis by providing a three-nucleotide sequence that precisely corresponds to specific amino acids or stop signals. This ensures that during translation, each codon is matched with its corresponding tRNA molecule carrying the appropriate amino acid. Any errors in reading or matching codons can lead to incorrect amino acid sequences, potentially resulting in malfunctioning proteins.
• Discuss how mutations in codons can impact protein function and lead to disease.
  • Mutations in codons can change the encoded amino acid sequence, leading to alterations in protein structure and function. For example, a missense mutation might replace one amino acid with another, potentially disrupting protein activity. In some cases, a nonsense mutation can create a premature stop codon, resulting in truncated proteins that may be nonfunctional or harmful. These changes can contribute to various diseases, including genetic disorders and cancers.
• Evaluate the significance of the start codon and its role in initiating translation within the context of the genetic code.
  • The start codon, AUG, is critically significant as it not only marks the beginning of translation but also encodes for methionine, establishing the first amino acid in a newly synthesized protein. This initiation is crucial for ensuring that proteins are synthesized with the correct starting point, influencing their overall structure and function. Without this precise starting point provided by the start codon, subsequent amino acids could be incorrectly assembled, leading to dysfunctional proteins and impacting cellular processes.

Related terms

Amino Acid: The building blocks of proteins, amino acids are organic compounds that combine to form proteins and are coded by codons.

mRNA (messenger RNA): A type of RNA that carries the genetic information from DNA to the ribosome, where it serves as a template for protein synthesis using codons.

Translation: The process by which the ribosome synthesizes proteins by decoding the mRNA codons into a specific sequence of amino acids.