Section C

1. Evaluate how regulatory element mutations (promoter, splice-site, poly-A tail) can impact gene expression and protein function.

A promoter mutation lowers or blocks binding of transcription factors. This reduces transcription and lowers mRNA output. Very weak promoter activity can remove the protein completely.

A splice-site mutation disrupts normal intron removal. This can create exon loss, exon gain or retention of introns. The mRNA may carry the wrong sequence. The protein may fold poorly or stop early.

A poly-A tail mutation reduces stability of the mRNA. The mRNA breaks down faster and produces less protein. Short mRNA survival lowers translation and weakens protein levels.

Together, these mutations change how much mRNA is made, how the mRNA is processed and how long it survives. This leads to clear changes in protein amount or protein quality.