A codon is composed of

Question

BlackTom AI · Accepted Answer

Topic at hand: the structure of a codon in genetic coding. 
Option 1: 'three sequential amino acids.' This is incorrect because amino acids are the building blocks of proteins, and codons are not composed of amino acids themselves; codons are read as sequences of nucleotides that correspond to amino acids during translation.
Option 2: 'three sequential nucleotides.' This is accurate because a codon is defined as a triplet of nucleotides in mRNA that specifies a single amino acid or a stop signal during translation. The codon’s three-nucleotide length is universal in the standard genetic code.
Option 3: 'two ribosomal subunits and a tRNA molecule.' This option describes components involved in translation initiation and elongation (the ribosome subunits and tRNA), not the composition of a codon. A codon is not made up of these molecules; rather, it is a sequence of nucleotides read by the ribosome.
Option 4: 'a TATA box and initiation site.' The TATA box is a DNA promoter element involved in transcription initiation, not a codon. The initiation site relates to transcription start, not codon structure. Hence this option mismatches the concept of a codon.
In summary, the concept tested is the structural definition of a codon, which is a triplet of nucleotides in the mRNA that codes for a specific amino acid or a stop signal. The other options either mix up the roles of nucleotides, amino acids, and molecular machinery, or reference elements not part of a codon’s makeup.

BIOL 1009 (001-006/050-055) Midterm Exam III

A codon is composed of

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