Final answer:
The switch and extension after the first jump results in the addition of a methyl-guanosine cap to the 5' end of the transcript, which is an essential step in mRNA processing known as 5' capping.
Step-by-step explanation:
The result of the switch and extension after the first jump is to add a methyl-guanosine cap to the 5' end of the transcript. This enzymatic addition, known as 5' capping, involves a capping enzyme that adds a 7-methylguanosine cap to the 5' end of a growing transcript through a phosphate linkage. This cap serves multiple functions: it protects the mRNA from degradation, aids in mRNA export from the nucleus, and is recognized by the ribosomes as a signal to begin protein synthesis. The capping occurs while the pre-mRNA is still being synthesized, which signifies the importance of this modification for the subsequent steps of mRNA processing and translation.