Prior to its export from the nucleus, what modifications must be made to a mRNA molecule in eukaryotic cells?
A) Addition of a poly-A tail and 5' cap.
B) Addition of intron regions to the mRNA.
C) Removal of the start codon and addition of the stop codon.
D) Addition of phosphate groups to energize the mRNA and ready it for translation.

Option A

Explanation:

Before the mRNA which has been processed from DNA is taken and transported to the ribosomes in the cytoplasm for the translation process, some modifications are made to the mRNA before transport. This includes

1. Capping: addition of 5'-5' phosphate bonds to the 5' terminus of the mRNA. Forms the cap structure that is essentials for binding to ribosomes via special proteins attached to the cap structure

2. Addition of poly(A) tail: a poly(A) addition signal (AAUAAA) is attached to the 3' terminus of the mRNA. They are important in translation initiation and degradation prevention

3. Splicing: this is likely the most remarkable processing in eukaryotes. It involves the removal of intron regions by excision from the present-mRNA and then ligating the exon regions together giving rise to the mRNA.

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