3) addition of the 7-methylguanosine cap to the 5 end
Explanation:
The 7-methylguanosine (m7G) cap is a modified methylated version of the Guanosine (G) nucleotide which is located on the 5′-terminus of the eukaryotic messenger RNA (mRNA). The m7G cap plays a key role in mRNA translation in eukaryotic organisms, from yeasts to mammals. During mRNA processing, m7G cap is added at the 5' end in order to protect mRNA from degradation by nuclease enzymes. Moreover, this cap also enables the proper attachment of the mRNA molecule to the ribosome during protein synthesis.
A closed circuit doesn't allow the flow of electrons. an open circuit does. example: if you turn off a switch in your house. you 'broke the circuit it is closed.
