Which of the following is a type of post-translational modification?

Post-translational modification refers to the chemical modifications that occur to a protein after its synthesis (translation) has taken place. Glycosylation is one of the most common types of such modifications, involving the addition of carbohydrate groups to a protein, which can influence its stability, localization, and function. This process is essential for the proper functioning of many proteins, especially in glycoproteins that play critical roles in cellular recognition and signaling.

In contrast, transcription and translation are processes involved in gene expression. Transcription is the process of synthesizing RNA from a DNA template, while translation is the subsequent synthesis of proteins from the mRNA transcript. Replication refers to the process of duplicating DNA, which is also separate from the post-translational modifications of proteins. Therefore, glycosylation stands out as a direct example of a modification that occurs specifically after a protein has been synthesized, aligning perfectly with the definition of post-translational modification.