Question

What are two main types of posttranscriptional modifications that take place in the mRNA of eukaryotes?The excision of the introns and the addition of a 7-mG cap to the 3' end.The addition of a poly-T sequence at the 5' end of the gene and the addition of a poly-U tail at the 3' end.The addition of a 7-mG cap at the 5' end of the transcript and the addition of a poly-A sequence at the 3' end of the message.The addition of a poly-A sequence at the 5' end and the addition of a 7-mG cap at the 3' end of the RNA transcript.

Answer 1

The correct answer is: The addition of a 7-mG cap at the 5' end of the transcript and the addition of a poly-A sequence at the 3' end of the message

These posttranscriptional processes are called:

• 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.