Which best describes a codon?
The Correct Answer and Explanation is:
The correct answer is: A codon is a sequence of three nucleotides in mRNA that codes for a specific amino acid.
Explanation:
A codon is a fundamental unit in the process of translation, which is part of protein synthesis. It refers to a sequence of three nitrogenous bases in a molecule of messenger RNA (mRNA). These three bases are read in sets of three, and each set (codon) corresponds to one specific amino acid, which are the building blocks of proteins.
In the central dogma of molecular biology, DNA is transcribed into mRNA, and this mRNA is then translated into a protein. During translation, the mRNA moves to the ribosome, where the sequence of codons in the mRNA dictates the sequence of amino acids that will be linked together to form a protein. This process occurs in the cytoplasm of a cell.
For example, a codon like AUG (adenine, uracil, guanine) is recognized as the start codon. This codon signals the beginning of the protein-coding sequence and codes for the amino acid methionine, which is the first amino acid in most proteins. In contrast, other codons correspond to different amino acids. For instance, UUU codes for phenylalanine, while GGC codes for glycine.
There are a total of 64 possible codons (4 nucleotides: adenine, cytosine, guanine, and uracil, raised to the power of 3). These codons include 61 that specify amino acids, and 3 that function as stop codons, signaling the end of the protein synthesis process.
In summary, a codon is crucial for the accurate translation of genetic information from mRNA to protein. It ensures that the correct amino acids are incorporated in the correct order to produce functional proteins, which are vital for cellular functions and the overall health of the organism.