Codon

Definition

A codon is a sequence of three nucleotides in mRNA that corresponds to a specific amino acid or a stop signal during protein synthesis. Codons play a crucial role in translating the genetic information encoded in DNA into functional proteins, linking the genetic code with the process of translation and tRNA's function in recognizing specific codons.

5 Must Know Facts For Your Next Test

1. There are 64 possible codons, made from combinations of the four nucleotides (adenine, cytosine, guanine, and uracil) found in RNA.
2. Codons are read during translation by ribosomes, which decode the mRNA sequence to synthesize proteins.
3. The genetic code is degenerate, meaning that multiple codons can encode the same amino acid, which helps protect against mutations.
4. Start codons, typically AUG, signal the beginning of protein synthesis, while three different stop codons (UAA, UAG, UGA) signal its end.
5. In eukaryotes, codons are often separated by non-coding sequences called introns that are removed during mRNA processing before translation.

Review Questions

• How do codons relate to the function of tRNA during translation?
  • Codons are critical for the function of tRNA because each tRNA molecule has an anticodon that is complementary to a specific codon on the mRNA strand. During translation, tRNA molecules recognize and bind to their corresponding codons based on this complementary pairing. This process ensures that the correct amino acids are added in the proper sequence to form a polypeptide chain, directly linking codons to protein synthesis.
• Discuss how the degeneracy of the genetic code impacts the accuracy of protein synthesis.
  • The degeneracy of the genetic code means that multiple codons can specify the same amino acid. This redundancy provides a safeguard against mutations; if a single nucleotide change occurs in a codon, it may still code for the same amino acid due to this overlapping coding system. As a result, this feature can enhance the accuracy and efficiency of protein synthesis since not all mutations will lead to a change in protein function.
• Evaluate the significance of start and stop codons in regulating protein synthesis.
  • Start and stop codons play essential roles in regulating protein synthesis by defining where translation begins and ends. The presence of a start codon like AUG ensures that ribosomes initiate protein production at the correct location on mRNA. Meanwhile, stop codons such as UAA, UAG, and UGA signal ribosomes to terminate translation once the complete polypeptide chain has been synthesized. This precise regulation is vital for producing functional proteins necessary for cellular processes and overall organism health.

Related terms

Amino Acid:

Organic compounds that serve as the building blocks of proteins, each amino acid is encoded by specific codons.

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

Stop Codon: A specific codon that signals the termination of protein synthesis, indicating that the ribosome should release the newly synthesized polypeptide chain.