RNA plays important roles in coding, decoding, regulating, and expressing genes. The three main types of RNA are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). mRNA comprises 5% of cellular RNA and carries coding information from DNA to sites of protein synthesis. tRNA transports amino acids to ribosomes and ensures the correct amino acid is added through complementary base pairing. rRNA makes up 80% of cellular RNA and is a major component of ribosomes, facilitating protein synthesis.

1. RIBO
NUCLEIC
ACIDS
PRESENTED BY,
KARAN N
M.S.c BIOTECHNOLOGY
JSSAHER

2. RNA - INTRODUCTION
.
• Ribonucleic acid (RNA) is a polymeric moleculeessential in various biological roles in coding,
decoding,regulation and expression of genes.
• Like DNA, RNA is assembledas a chain of nucleotides,but unlike DNA, RNA is found in nature as
a single strand foldedonto itself,rather than a paired doublestrand.
• RNA moleculesplay an active role within cellsby catalysing biological reactions, controlling
gene expression,or sensing and communicating responsesto cellular signals.
• One of these active processesis protein synthesis, a universal function in which RNA molecules
direct the synthesis of proteins on ribosomes.
• In 1961French scientists Francois jacob and Jacques monod hypothesizedthe existence of an
intermediary between DNA and its protein products.
• The structure of the RNA moleculewas first described by R.W. Holley in 1965.

3. RNA - STRUCTURE
.
• RNA is typically single stranded and is made of ribonucleotidesthat are linked by
phosphodiesterbonds.
• The strand has a 5´end with a phosphate group and 3’ end with hydroxyl group.
• A ribonucleotidein the RNA chain contains ribose( the pentose sugar),with carbons numbered 1
to 5. one of the four nitrogenous bases(A,U, G, and C) that is attached to 1st position and a
phosphate group that is attached to 3rd position of one ribose and 5th position of the next.
• The phosphate groupshave negative charge making RNA negative charged molecule.
• The bases form hydrogen bonds between cytosine and guanine, between adenine and uracil and
between guanine and uracil.
• An important structural component of RNA that distinguishes it from DNA is the presence of a
hydroxyl group at the 2nd position of the ribose sugar.

4. RNA - STRUCTURE
.

5. RNA – II STRUCTURE
.
FLEXIBILITY
INCREASES
STABILITY!!!

6. RNA - TYPES
.
In both prokaryotes and eukaryotes,there are three main types of RNA-
5%
80%
15%
rRNA
tRNA
mRNA

7. Messenger RNA
.
• MessengerRNA comprises only 5% of the RNA in the cell.
• It is the most heterogenoustype of RNA in terms of size and base sequence.
• All members of this class function as messengerscarrying the information in a gene to the
protein synthesizing machinery.
• the mRNA moleculesare formed with the help of DNA template during the process of
transcription.
• The sequence of nucleotides in mRNA is read in the form of codons.
• A codon is made up of 3 nucleotides.
• The mRNA is formedafter processing of heterogenous nuclear RNA.
• The 5’ terminal end is capped by 7 methyl guanosine triphosphate cap.
• The cap is involvedin the recognition of mRNA by the translating machinery.
• It stabilizesmRNA by protecting it 5’ exonuclease activity.

8. mRNA-STRUCTURE
.
• The 3’ end of most mRNAs have a polymerof adenylate residues.
• This tail prevents the attack by 3’ exonucleases.
• On both 5’ and 3’ end there are non coding sequences which are not translated(NCS).
• The intervening region between non coding sequences present between 5’ and 3’ is called
coding region. This region encodes for the synthesis of a protein.

9. mRNA-PROCESSING
.
Eukaryotic genes
are
monocistronic!!!

10. TRANSFER RNA
.
• Transfer RNA are the smallest of the three major species of RNA molecules.
• On average they have 74-95nucleotide residues.
• They are synthesized by the nuclear processingof a precursor molecule.
• They transfer the amino acids from cytoplasm to the protein synthesizing machinery, hence the
name tRNA.
• They are also called adapter molecules,since they act as adapters for the translation of the
sequence of nucleotidesof the mRNA in to specific amino acids.
• There are at least 20 species of tRNA one corresponding to each of the 20 amino acids required
for protein synthesis.
• They are easily soluble,hence they are also known as solubleRNA or sRNA.

11. TRANSFER RNA
.
• Primary structure- the nucleotide sequence of all the tRNA moleculesallows for the extensive
intrastand complementarity that generates a secondary structure.
• Secondary structure- Each single tRNA shows extensive internal base pairing and acquires a
clover leaf like structure. The structure is stabilized by hydrogen bonding between the bases
and is a consistent feature.

12. TRANSFER RNA
.
All tRNA contain 5 main arms or loops.Which are as follows:
• Acceptor arm
1. The acceptor arm is at 3’ end and It has 7 base pairs.
2. The 3’ OH group terminal of adenine binds with carboxyl group of amino acids, the tRNA bound to
amino acid is called amino acyl tRNA.
• Anticodon arm
1. Lies at the oppositeend of acceptor arm and it is 5 base pairs long.
2. It binds to codons in mRNA during translation.
• DHU arm - Serves as recognition site for amino acyl tRNA synthase that adds amino acid to the
acceptor arm.
• T arm- it is involved in binding of tRNA to the ribosomes
• Extra arm or variable arm- about 75% of tRNA moleculepossessa short variable arm.

13. RIBOSOMAL RNA
.
• rRNAs are found in the ribosomesand account for 80% of the total RNA present in the cell.
• Ribosomesare composedof a large subunit called the 50S and a small subunit called the 30S in
prokaryotesand 60S and 40S in eukaryoteseach of which is made up of its own specific rRNA
molecules.
• Different rRNAs present in the ribosomesinclude small rRNAs and large rRNAs, which belong to
the small and large subunits of the ribosome,respectively.
• rRNAs combine with proteins and enzymes in the cytoplasm to form ribosomes,which act as the
site of protein synthesis. These complex structures travel along the mRNA moleculeduring
translation and facilitate the assemblyof amino acids to form a polypeptidechain.
• They interact with tRNAs and other moleculesthat are crucial to protein synthesis.
• In bacteria, the small and large rRNAs contain about 1500 and 3000 nucleotides,respectively,
whereas in humans, they have about 1800 and 5000 nucleotides,respectively.However, the
structure and function of ribosomesis largely similar across all species.

14. RIBOSOMAL RNA
.
S stands for
svedberg constant.

15. OTHER TYPES OF RNA
.
Small nuclear
RNA (snRNA)
siRNA micro RNA
(miRNA)
Ribozymes (RNA
enzymes)
Double-stranded
RNA (dsRNA)
snRNA is involved in
the processing of pre-
messenger RNA (pre-
mRNA) into mature
mRNA. They are very
short, with an average
length of only 150
nucleotides.
siRNA (20-25 nt) are
often produced by
breakdown of viral
RNA, though there are
also endogenous
sources of siRNAs. An
mRNA may contain
regulatory elements
itself, such as
riboswitches, in the 5'
untranslated region or
3' untranslated region;
these cis-regulatory
elements regulate the
activity of that mRNA.
miRNA (21-22 nt) is
found in eukaryotes,
and acts through RNA
interference (RNAi).
miRNA can break
down mRNA that it is
complementary to,
with the aid of
enzymes. This can
block the mRNA from
being translated, or
accelerate its
degradation.
RNAs are now known
to adopt complex
tertiary structures and
act as biological
catalysts. Such RNA
enzymes are known
as ribozymes.
One of the first
ribozymes to be
discovered was
RNase P, a
ribonuclease that is
involved in generating
tRNA molecules from
larger, precursor
RNAs.
This type of RNA has
two strands bound
together, as with
double-stranded DNA.
dsRNA forms the
genetic material of
some viruses..

16. REFERENCES

17. THANK
YOU