Page 48 - Cell biology PDG 2024

Capping is the addition of a methylated guanine cap to the 5′ end of
mRNA. Its presence is important for the recognition of the molecule
by ribosomes, and to protect the immature molecule from being
degreded by RNAases in the cytoplasm

 Polyadenylation

It is the addition of a poly (A) tail to the 3′ end of mRNA. The poly
(A) tail consists of multiple molecules of adenosine monophosphate.
This stabilizes RNA, which is necessary as RNA is much more
unstable than DNA.

 Splicing

It involves:

 Introns (non-coding sequences) are removed via spliceosome
excision

 Exons (coding sequence) are then joined together by ligation

Difference between DNA and RNA

Bases DNA RNA
structure
sugar A,G,C,T A,G,C,U
location
Life span antiparallel Hair pin loop
process Deoxyribose ribose
strands nucleus Nucleus or cytoplasm
types long short
transcription translation
Double strand Single strand
Nuclear DNA mRNA, tRNA, siRNA
mt DNA rRNA, miRNA

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