RNA molecules are single-stranded nucleic acids that play a major role in protein synthesis by being involved in the transcription, decoding, and translation of the genetic code. RNA contains nucleotides with nitrogenous bases (A, G, C, U), the pentose sugar ribose, and a phosphate group. There are different types of RNA including transfer RNA (tRNA), ribosomal RNA (rRNA), and messenger RNA (mRNA) which are involved in protein synthesis. RNA undergoes processes like transcription, capping, polyadenylation, and splicing to produce mature mRNA for translation into proteins.

1. LET’STALK ABOUT
RIBONUCLEIC ACIDS (RNA’S)
By Mwikisa Mayungano 马克思
8th June 2017-GENETICS-

2. RNA(ribonucleic
acid);

7. What is RNA?
-RNA molecules are single stranded nucleic acids
composed of nucleotides.
-Plays a major role in protein synthesis. How? It’s
involved in the transcription, decoding, and translation
of the genetic code to produce proteins.
-RNA nucleotides contain three components:
A Nitrogenous Base
A Five-CarbonSugar
A Phosphate Group

8.  RNA nitrogenous bases: Adenine (A), Guanine (G), Cytosine
(C) and Uracil (U).
 The five-carbon (pentose) sugar: Ribose.
 Phosphate group: RNA molecules are polymers of
nucleotides joined to one another by covalent bonds between
the phosphate of one nucleotide and the sugar of another.
These linkages are called phosphodiester linkages

9. RNA STRUCTURE
 Back bone is a sugar and phosphate group
 Nitrogenous bases linked to sugar moiety project from the backbone
 Nitrogenous bases are linked to pentose sugar through N-glycosidic
linkage to form a nucleoside
 Phosphate group is linked with 3’OH of nucleoside through
phosphoester linkage
 2 nucleotides are linked through 3’-5’-phosphodiester linkage to form
a dinucleotide
 More and more such groups will be linked to form a poly nucleotide
chain
 Such a polymer has a free phosphate moiety at 5’ end of ribose sugar
and it is called as 5’-end of polynucleotide chain
 At other end, ribose has free 3’-OH group which is called as the 3’-end
of polynucleotide chain
 In RNA, every nucleotide has an additional-OH present at 2’-position
of ribose.

10. Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Messenger RNA (mRNA)
The others are;
o small nuclear RNA (SnRNA),
o micro RNA(mi RNA) and
o small interfering RNA(Si RNA) and
o heterogeneous nuclear RNA (hnRNA).
RNA CLASSIFICATION

20. transcription - A process that involves
transcribing genetic information from DNA to RNA
RNA polymerases.

21. a toxin found
in some types of mushrooms.

22.  INITIATION

23.  RNA ELONGATION:
TERMINATION:

25. a) Capping
b) Polyadenylation
c) Splicing.

26. • CAPPING:The process of modifying the 5'-end of eukaryotic mRNA with 7-methylguanine.
Guanylyl transferase catalyzes the linking of 7'-methylguanylate to the mRNA through a 5' to 5'
triphosphate bridge.The capping positions the mRNA onto the 40S preinitiation complex and
protects it from exonuclease activity.
• POLYADENYLATION: is the addition of a chain of adenylate residues, poly A tail, to the 3'
terminus of mRNA. After the RNA is cut, an enzyme, poly A polymerase, catalyzes the
polymerization of adenylates.The poly A tail slows the exonucleolytic degradation of mRNA, once
the tail is removed mRNA is quickly degraded.
• SPLICING: is the removal of noncoding sequences, derived from the DNA template, from the
hnRNA to form a functional mRNA.
Noncoding sequences - introns
Coding sequences - exons.
- All introns have the sequence GU at their 5' ends andAG at their 3' ends.
-The guanyl residue at the 5' end of the intron is linked by a 2' to 5' phosphodiester linkage to an
adenylate residue within the intron.
-The result is a lariat (loop) structure and the release of the 3' end of the first exon.
-The 3' end of the intron is spliced by an enzyme, Spliceosome-which releases the loop and frees
the 5' end of the second exon.The exons are then joined together.