Final answer:
Yes, a 7-methylguanosine cap is necessary for an mRNA to leave the nucleus as it protects the mRNA from degradation and assists in translation.
Step-by-step explanation:
Yes, a 7-methylguanosine cap is necessary for an mRNA to leave the nucleus. The cap is added to the 5' end of pre-mRNAs and serves two main functions:
- Protects the mRNA from degradation.
- Assists in translation by helping the initiation complex recognize the start codon.
Without the cap, the mRNA may be degraded and it would be more difficult for the ribosome to locate the start codon, leading to inefficient translation.