During RNA processing a (n) _____ is added to the 5′ end of the RNA.
A: 3′ untranslated region
B: A long string of adenine nucleotides
C: 5′ untranslated region
D: Coding segment
E: Modified guanine nucleotide
The correct option is E.
During RNA processing a (n) modified guanine nucleotide is added to the 5′ end of the RNA.
In Eukaryotes, pre-mRNA receives a 5′ cap and a 3′ poly (A) tail before the removal of introns, and the mRNA is considered ready for translation.
Gene expression happens differently in Bactria and eukaryotes, such as humans.
In a eukaryotic cell, a pre-mRNA is produced in the nucleus by the transcription of a region of DNA from a linear chromosome.
In this transcription, splicing and addition of 5′ cap a poly-A tail occur while it remains in the nucleus to form a mature mRNA. The mature mRNA is transferred to the cytosol from the nucleus to form a polypeptide at a ribosome.
The DNA in the cytosol converts into a circular chromosome, and it is being transcribed to make an RNA. The RNA can be associated ribosome, and it can start translation to form a polypeptide.
RNA transcripts in bacteria are ready to act as mRNAs and get translated into proteins immediately.
In eukaryotes, a pre-mRNA needs to go through some more steps to become an actual m-RNA. These steps are:
- Addition of a 5′ cap to the beginning of the RNA
- Addition of a poly-A tail to the end of the RNA
- Chopping out of introns and pasting together of the remaining sequences (exons)
When all of these stages get completed, the mature RNA came out of the nucleus to form a protein.
5′ cap and poly-A tail:
The addition of chemical groups converts both sides of a pre-mRNA. The chemical group at the beginning (5′ end) is known as a cap, while the group which is added at the end (3′ end) of a pre-mRNA is called a tail.
The cap and the tail, both protect the transcript and help in its exportation from the nucleus. It is translated on the ribosomes present in the cytosol.
The 5′ cap is a modified guanine (G) nucleotide, which protects the transcript from being damaged. It also helps the ribosome attach to the mRNA and start reading it to make a protein.