What are two main types of posttranscriptional modifications that take place in the mrna of eukaryotes?

Addition of poly A tail and and addition of 5' cap

Explanation:

In eukaryotes, many post-transcriptional modification takes place like 5' capping, polyadenylation, and splicing. In 5' capping 7-methyl guanosine is added toward the 5' end of mRNA by the action of a enzyme called guanyl transferase. This cap protects mRNA from degradation.

In polyadenylation up to 250 adenosine nucleotides are added at the 3' end of the mRNA and it is called poly-A tail. Poly A polymerase is the enzyme that is responsible for polyadenylation.  

Therefore two main post transcription modifications are 5' capping and polyadenylation.

answer; ///i do believe that the correct answer is (c) hold atoms together to form compound;

hydroxyl -oh

alcohols, always polar, can form hydrogen bonds with h2o molecules

carboxyl -cooh  

cargoxylic acids, has acidic properties which is a source of hydrogen ions, found in cells in ionized for with a charge of oh-1

carbonyl > co

ketone if within skeleton, aldehyde if group is at the end of skeleton, k & a may be structural isomers, it determines 2 sugars (ketose & aldose)

amino -nh2

amines, acts as a base, it can pick up h+ ions from surrounding solution, ionized with charge of 1+

methyl ch2

addition to rna/dna affects and gene expression

phosphate -opo3 ²⁻

organic phosphates, contributes to negative charge to, molecule that it is a part of, and potential to react with h20

sulfhydryl -sh

thiols, cross-linking stabilize the protein, and it is structure