Codon

Definition

A codon is a sequence of three nucleotides in DNA or RNA that corresponds to a specific amino acid or serves as a stop signal during protein synthesis. Each codon is crucial in the process of translating genetic information into functional proteins, as they determine the order in which amino acids are added to a growing polypeptide chain. The codon is a fundamental unit of the genetic code and plays a key role in the translation process within cells.

5 Must Know Facts For Your Next Test

1. There are 64 possible codons, but only 20 standard amino acids, leading to redundancy in the genetic code, where multiple codons can specify the same amino acid.
2. Codons are read in a non-overlapping manner during translation, meaning that each nucleotide is part of only one codon.
3. Start codons, like AUG, signal the beginning of protein synthesis and specify the amino acid methionine, while stop codons signal the termination of translation.
4. Codons are present in messenger RNA (mRNA), which is transcribed from DNA and serves as the template for protein synthesis.
5. Mutations can affect codons and potentially change the resulting protein, which can lead to variations in traits or diseases.

Review Questions

• How do codons determine the structure and function of proteins?
  • Codons determine the structure and function of proteins by specifying the sequence of amino acids during translation. Each three-nucleotide codon corresponds to a specific amino acid, and the order of these codons in mRNA dictates how the amino acids are arranged in the resulting protein. This sequence is critical because even small changes in codons can lead to significant differences in protein structure and function, influencing an organism's traits.
• Discuss how mutations in codons can affect protein synthesis and lead to genetic disorders.
  • Mutations in codons can lead to changes in the amino acid sequence of proteins, which may disrupt their normal function. For instance, if a mutation changes a codon from coding for one amino acid to another, it can alter the protein's shape and stability, potentially leading to loss of function or gain of harmful function. Some genetic disorders arise when such mutations lead to nonfunctional proteins or proteins that interfere with normal cellular processes.
• Evaluate the significance of redundancy in the genetic code regarding evolutionary biology.
  • The redundancy in the genetic code, where multiple codons can specify the same amino acid, has significant implications for evolutionary biology. This feature provides a buffer against mutations; not all changes in DNA will result in altered proteins because some mutations may still code for the same amino acid. This redundancy allows for greater genetic variation without detrimental effects on protein function, contributing to adaptability and evolution within populations as they respond to environmental pressures.

Related terms

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

anticodon: A sequence of three nucleotides in transfer RNA (tRNA) that is complementary to a specific codon in mRNA, allowing for the correct amino acid to be added during protein synthesis.

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