What is a codon?

What is a codon?

• A. A two-nucleotide sequence in DNA.
• B. A one-nucleotide sequence in mRNA.
• C. A three-nucleotide sequence in DNA that signals replication.
• D. A three-nucleotide sequence in mRNA that codes for an amino acid.

Answer: (D)

A codon is a three-nucleotide sequence in messenger RNA that determines which amino acid will be added next during protein synthesis. In the flow of genetic information, DNA is transcribed into mRNA, and the ribosome reads the mRNA in sets of three bases (codons) from 5' to 3'. Each codon corresponds to a specific amino acid (or a stop signal) carried by tRNA, guiding the assembly of the polypeptide chain. There are 64 possible codons (4 options per position, three positions), providing the code for all amino acids with some redundancy. A start codon, like AUG, marks the reading frame and begins translation, while stop codons terminate it. This makes codons a property of the mRNA sequence, not a feature of DNA or replication signals.

A codon is a three-nucleotide sequence in messenger RNA that determines which amino acid will be added next during protein synthesis. In the flow of genetic information, DNA is transcribed into mRNA, and the ribosome reads the mRNA in sets of three bases (codons) from 5' to 3'. Each codon corresponds to a specific amino acid (or a stop signal) carried by tRNA, guiding the assembly of the polypeptide chain. There are 64 possible codons (4 options per position, three positions), providing the code for all amino acids with some redundancy. A start codon, like AUG, marks the reading frame and begins translation, while stop codons terminate it. This makes codons a property of the mRNA sequence, not a feature of DNA or replication signals.