A Level Biology Practice Exam 2025 - Free A Level Biology Practice Questions and Study Guide

The genetic code sequence is composed of codons, which are specific sequences of three nucleotides that correspond to particular amino acids or serve as stop signals within the process of translation during protein synthesis. Each codon provides the necessary information to build a specific part of a protein by dictating which amino acid should be added to the growing polypeptide chain.

While nucleotides are the building blocks of nucleic acids and play a critical role in forming codons, they are not themselves the components of the genetic code sequence as defined by its functional expression during protein synthesis. Amino acids are the result of the translation of codons and make up proteins, but they are not part of the genetic code sequence. Chromosomes are structures that organize and contain the entire genetic material within a cell, but they are not the components of the genetic code sequence itself. Thus, identifying codons as the components of the genetic code sequence is correct due to their direct role in encoding the information required for synthesizing proteins.