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Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?
A. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.
B. A translation stop codon is added at the 3' end of the pre-mRNA.
C. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
D. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.
E. Coding sequences called exons are spliced out by ribosomes.

Respuesta :

The processing that takes place before a mature mRNA exits the nucleus,

A translation stop codon is introduced to the pre-mRNA's 3' end.

c. The 3' end of the pre-mRNA gets a poly-A tail (50–250 adenine nucleotides) attached to it.

d. Ribosomes splice out coding segments referred to as exons.

  • In eukaryotes, RNA must leave the nucleus through the nuclear membrane's pores and reach the cytoplasm to undergo translation during protein synthesis. The 3' Poly-A tail, 5' capping, and pre-mRNA splicing are the mRNA's departure mechanisms.
  • The 5'capping procedure involves adding a 7-methylguanosine cap through phosphate linkage to the 5' end of the mRNA. This procedure helps to start translation processes and prevents mRNA degradation.

The cleaving of pre-mRNA and attachment of about 200 A nucleotides, or the 3'poly (A) tail, to the mRNA by the poly (A) polymerase enzyme protein complex is known as the 3' Poly-A tail step. This facilitates the transfer of mRNA to the cytoplasm, stops pre-mRNA degradation, and starts translation.

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