mRNA Capping and Polyadenylation

Two important post-transcriptional modifications to messenger RNA include 5’ capping and polyadenylation. It should be noted that these additions only take place for eukaryotic cells, such as those found in animals and plants. After mRNA has been synthesized, it is processed by enzymes that add a guanine nucleotide to its 5’ end and a chain of several adenine nucleotides to its 3’ end. The guanine nucleotide, denoted here as GTP, is attached as the 5’ cap of the mRNA and is linked to the molecule by a capping enzyme, not shown. A special enzyme called a poly-A-polymerase represented by the white sphere, adds the chain of adenines, or poly(A) tail, to the 3’ end of the RNA. In eukaryotes, these modifications are involved in translation initiation and stability of the mature RNA molecule.

Question 1: What are two important processes in post-transcriptional modification of RNA molecules?
  1. Transcription and transfer RNA stitching.
  2. 5’capping and polyadenylation.
  3. 3’capping and polyadenylation.
  4. 4’capping and polyadenylation.


Answer 1 Answer – 5’capping and polyadenylation

Question 2: 5’ capping is the process of adding a(n) _____________ to the 5’ end of an RNA molecule.
  1. adenine nucleotide
  2. cytosine nucleotide
  3. guanine nucleotide
  4. uracil nucleotide


Answer 2 Answer – (c) guanine nucleotide

Question 3: Which enzyme is responsible for polyadenylation?
  1. Poly-A-polymerase.
  2. PolA-polymerase.
  3. Polyadenylase.
  4. Trypsin.


Answer 3 Answer – (a) Poly-A-polymerase

Question 4: What is polyadenylation?
  1. Making a lot of adenylase.
  2. Addition of a chain of several adenine nucleotides to the 3’ end of RNA.
  3. Addition of a chain of several adeninyl nucleotides to the 3’ end of RNA.
  4. Building of polymerases.


Answer 4 Answer - (b) Addition of a chain of several adenine nucleotides to the 3’ end of RNA.

Question 5: What is the goal of post-transcriptional modification of RNA molecules?
  1. Making DNA translate the RNA molecules.
  2. Making RN A translate the DNA molecules.
  3. Transcription initiation and improving the stability of the mRNA molecules.
  4. Translation initiation and improving the stability of the mRNA molecules.


Answer 5 Answer – (d) Translation initiation and improving the stability of the mRNA molecules.