Final answer:
b) Inability to exit the nucleus. The absence of the 5' methyl guanosine cap on mRNA would likely lead to instability, difficulty in nuclear export, and issues with translation.
Step-by-step explanation:
b) Inability to exit the nucleus. The addition of a 5' methylguanosine cap, commonly referred to as the 5' cap, is a crucial modification to mRNA molecules during transcription in eukaryotic cells. This modification involves the addition of a methyl group to the guanosine nucleotide at the 5' end of the mRNA. The 5' cap serves multiple functions, one of which is facilitating the export of mRNA from the nucleus to the cytoplasm. Without the 5' cap, the mRNA may be unable to bind to the necessary export factors and transport proteins, resulting in its retention within the nucleus. This hinders the progression of gene expression, preventing the mRNA from participating in translation processes in the cytoplasm.