Question

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Question 14 (1 point) Eukaryotes modify a primary RNA transcript to generate a final mRNA product. Which of the following modifications is something that occurs to eukaryotic RNA (which one is correct): OA) removing exons from the transcript B) adding introns into the transcript C) adding a poly(A) tail to the transcript by poly(A) polymerase OD) adding start codons to the transcript after its synthesis E) removing a 5' cap from the transcript

Answer 1

Question 14-

ANSWER - (c) adding a poly (A) tail to the transcript by poly (A) polymerase.

EXPLANATION--

• Transcription is occurs in the nucleus, where DNA is used to produce RNA molecule.
• mRNA is used as template for synthesizing proteins in the cytoplasm of cell. Before the mRNA make it way out of nucleus, it must undergoes several modifications.
• These modifications are three type -

1. 5'- guanosine triphosphate capping
2. Polyadenylation of 3' - end
3. Spilicing

POLYADENYLATION OF 3'- END --

• most eukaryotic mRNA have a chain of 40 t0 200 adenine nucleotide attached to 3'- end.
• These are not transcribed  
• In this modifications ,the 3'- end of pre mRNA are removed and a series of adenosine nucleotide is attached.
• This process is called polyadenylation of 3'- end.
• It provides stability and facilitate the exit of mRNA from nucleus.
• The enzyme poly (A) polymerase help on these process.
• After the mRNA enters the cytoplasm, the poly A tail is gradually shortened.

Other options

Option (A) - removing exons from the transcript.

Explanation- it is wrong statement. Introns are removed from transcript.

Option(B) - adding introns to the transcript.

Explanation- it is wrong statement. Exons are added . Introns are cut out from transcript.

Option (D) -adding start codon to the transcript after it's synthesis.

Explanation-it is also wrong.

Option (E) -removing a 5'- cap from transcript.

Explanation- it is incorrect. We add 5'- cap to transcript.