Question

Which of the following lists steps of mRNA production in eukaryotes in the correct order?Transcription, 5' cap addition, addition of poly-A tail, passage through nuclear membrane, exon splicingTranscription, addition of poly-A tail, 5' cap addition, exon splicing, passage through nuclear membrane5' cap addition, addition of poly-A tail, exon splicing, passage through nuclear membrane, transcriptionTranscription, 5' cap addition, addition of poly-A tail, exon splicing, passage through nuclear membrane

Answer 1

The correct order is: Transcription, 5' cap addition, addition of poly-A tail, exon splicing, passage through nuclear membrane

mRNA must undergo posttranscriptional modification in order to produce a mature, functional RNA molecule that can then leave the nucleus and be translated.

• 5’cap addition or 5’ capping - It protects the mRNA from 5' degradation by exonucleases. Cap is also involved in ribosomal binding.

• Polyadenilation or addition of poly(A) tail – It also protects mRNA from degradation of 3’exonucleases. A long poly(A) tail can also increase translation

• Exon splicing-This is a process in which introns are removed from the pre-mRNA and the exons connected to form a continuous molecule of mature mRNA.