Question

What modifications occur in eukaryotic mRNA? In t-RNA? In r RNA?

Answer 1

Answer

m (messenger) - RNA modifications:

• In eukaryotes mRNA is monocistronic ie: one mRNA will code for only one polypeptide.

1. 5’ capping - addition of the 7 methyl guanosine to cap the 5’ 3’ end
2. Polyadenylation- Addition of the poly- A tail at the 3’ end
3. Splicing- To remove non coding sequence (intron) and joining together of exons to make mature mRNA.

r (ribosomal)- RNA modifications:

1. 45 S precursor RNA is removed to 41 S at the 5’end Then this 41 S cuts to make 2 parts such as 20 S precursor of 18 S rRNA and 32 S precursor of the 5.8 S and 28 S.
2. Then the 3’ end of 20 S precursor removed to yield a mature 18 S rRNA
3. 32 precursor is cut to get the 5. 8 as well as 28 S rRNA.Then both this associate by base pairing.

t- RNA modifications:

• ​​​​​​​​​​​​​​Four types of process is needed to modify the pre- tRNA to become mature tRNA

1. ​​​​​​​REMOVING OF EXTRA SEGMENT at the 5’ end by the RNase P.
2. REMOVING INTRON in from the anticodon loop by a process called splicing
3. REPLACING OF TWO RESIDUES OF U BY CCA at the 3’ end.
4. MODIFYING FEW RESIDUES to make characteristics bases.

​​​​​​​Hope it will helpful to you. Thank you

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