Answer: Post-Transcription and Post-Translation Modifications
Step-by-step explanation:
Following transcription, our cells have to go through RNA maturation which includes splicing out the introns before it can enter the cytoplasm. Alternative splicing is a post-transcriptional modification that can lead to an alternative protein products. Some introns may be left in while others are cut out etc. Refer to pic.
Following translation, a protein has been formed but can undergo post-translational modifications. Post-translational modifications refer to amino acid side chain modification in some proteins after their biosynthesis. There are more than 400 different types affecting many aspects of protein functions.
These are two ways that explain why there are more unique proteins than genes that encode them.