Imagine that a eukaryotic cell carries a mutation that causes the 5' cap to rarely be added to primary transcripts. What would be the result of such a mutation?

As a result of that mutaton, RNA transcripts would be less stable because 5' cap has a function to prevent degradation by exonucleases. Also RNA transcripts would stay in nucleus because 5' cap regulates nuclear export. Translation would be adversely affected because 5' cap promotes translation.