How does the mRNA used in protein synthesis differ from the original RNA transcript?

What is the apparent function of each of the alterations or modifications?How does the mRNA used in protein synthesis differ from the original RNA transcript?
The mRNA that is exported from the nucleus following transcription differs from the original RNA transcript in two ways ...





(1) The original RNA transcript contains both coding (exons) and noncoding (introns) regions. Surprisingly, most of our DNA is composed of noncoding, ';junk'; DNA. The cell does not want to translate this into protein, so spliceosomes cleave the introns out and DNA ligases glue the exons back together.





(2) To protect the mRNA and prevent it from being degraded by proteases in the cytosol, the nucleus attaches two things to the mRNA: a 5'G-cap, which is basically just a series of guanine nucleotides, and a poly-A tail, a series of adenine nucleotides.How does the mRNA used in protein synthesis differ from the original RNA transcript?
In eukaryotes the gene may be comprised of introns and exons. The introns will be removed and the exons joined, via a process called splicing, to form the mature-mRNA from the pre-mRNA.
The mRNA is translated from the RNA transcript--all Cs will turn into Gs and all As will be Us and vice versa. Also keep in mind the 5'-3' polarity.

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