RNA differs from DNA in three main ways - it contains ribose instead of deoxyribose, contains the base uracil instead of thymine, and is usually single-stranded. Despite being single-stranded, RNA molecules often exhibit double-helical structures through base pairing between complementary sequences that can form stem-loop or pseudoknot structures. There are several types of RNA including messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), microRNA (miRNA), and small nuclear RNA (snRNA) that have different functions in protein synthesis, splicing, and gene regulation. Alternative splicing of pre-mRNA allows a single gene to code for multiple proteins.

1. Presented by :
Gohil Sanjay B.
M.SC.Sem-3 (BOTANY)

2. CONTENTS
• INTRODUCTION
• Structure of RNA
• Synthesis
• TYPES OF RNA
• Function of different RNA
• RNA usually Single-Stranded
• RNA chains fold back
• Alternative form of RNA splicing

3. Introduction of RNA
• Back bone is 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.

4. • 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

5.  Ribonucleic acid, or RNA is one
of the major biological
macromolecules that are
essential for all known forms of
life (along with DNA and
proteins).
 Each nucleotide in RNA
contains a ribose sugar, with
carbons numbered 1' through
5'. A base is attached to the 1'
position, in general, adenine
(A), cytosine (C), guanine(G),
and uracil (U).

6. Structure of RNA

7. Synthesis
• Synthesis of RNA is usually catalyzed by an enzyme—
RNA polymerase.
• By using DNA as a template.
• The process is known as transcription .
• There are also a number of RNA-dependent RNA
polymerases that use RNA as their template for
synthesis of a new strand of RNA .
• A number of RNA viruses (such as poliovirus) use this
type of enzyme to replicate their genetic material

8.  Messenger RNA (m RNA)
 Ribosomal RNA ( r RNA)
 Transfer RNA (t RNA)
 Micro Rna ( mi RNA)
 Small Interfering RNAs ( Si RNAs)
 Small nuclear RNA (Sn RNA)
 Guide RNA
 COMPLEMENTRY RNA (C RNA)

9. m RNA- Messenger RNA
• Messenger is RNA is a large of RNA molecules
that convey genetic information from DNA to the
ribosome where they specify the amino acid
sequence of the protin products of gene
expression.

10. • It contains ribose instead of deoxyribose it
contains uracil instead of thaymine.
• It is coded so that every three nucleotides
corresponding one amino acid.
• In eukaryotic cells once precursor mRNA has been
transcribed from DNA it's processed to mature
mRNA.
• This removes it's introns -noncoding section s of
the pre mRNA.

11. rRNA
• rRNA:- Ribosomal RNA
• In molecular biology ribosomal, ribonucleic acid is
the RNA component of the ribosomal & essential
for protein synthesis in all living organisms.
• rRNA is extremely abudant & makes up 80% of
10mg/ml RNA found in a typical eukaryotic
cytoplasm.
r-RNA

12. • Eukaryotic ribosomal contain four different rRNA
molecules: 18s,5.8s,28s & 5s rRNA.
• rRNA molecules are synthesized in the nucleus.
• In cytoplasm ribosomal RNA & protein combine to from a
nucleoprotein called a ribosomes.

13. t-RNA
• Transfer ribonucleic acid is type of RNA molecule
that helps decode a m-RNA sequence into protein.
• t-RNA function at specific sites in the ribosome
during translation which is process that
synthesized a protein from an mRNA molecule.

14. • tRNA is a small RNA chain of about 80 nucleotides.
• In transfers specific amino acid to growing
polypeptide chain at the ribosomal site of protein
synthesis during translation.
• It has sites for amino acid attachment & anticodon
region for codon recognition.

15. • mRNA chain through hydrogen bonding.
• The tertiary structure of tRNA is best described
as a compact 'L' shape.
• The anticodon is a single - stranded loop at the
bottom of the figure which later base-pairs with
the triplet codon.
• The amino acid is attached to the terminal A on
the upper right .
• The active sites are maximally separated.

16. Mi RNA (micro Rnas)
• microRNAs, short non cooding RNAs present in all
living organisams, have been shown to regulate
the expression of at least half of all human genes.
• These single-stranded RNAs expert their regulatory
action by binding messenger RNAs expert their
regelatory action by binding messenger RNAs and
preventing their translation into protein.

17. Small interfering RNA (siRNA)
• Small interfering RNA (siRNA) are 20-25 nucleotide-long
double-stranded RNA molecules that have a variety of roles
in the cell.
• They are involved in the RNA interference (RNAi) pathway,
where it interferes with the expression of a specific gene by
hybridizing to its corresponding RNA sequence in the target
mRNA.
• This then activates the degrading mRNA. Once the target
mRNA is degraded, the mRNA cannot be translated into
protein.

18. Small Nuclear RNAs (snRNAs)
• Sn RNA s are involved in the process of splicing
(intron removal) of primary transcript to form
mature m RNA.
• The Sn RNA s form complexes with proteins to
form Ribonucleoprotein particles called snRNPs

19.  Guide RNA (gRNA) : are RNA genes that function
in RNA editing, found in mitochondria by inserting
or deleting stretches of uridylates (Us) .
The gRNA forms part of editosome and contain
sequences to hybridize to matching sequences in
the mRNA to guide the mRNA modifications.
 Complementary RNA( cRNA ): viral RNA that is
transcribed from negative sense RNA and serves as
a template for protein synthesis Negative sense
RNA viral RNA with a base sequence
complementary to that of mRNA during replication
it serves as a template to the transcription of viral
complementary RNA

20. Function of defferent RNA
• mRNA: It carries genetic formation of DNA ( Gene )
for protein synthesis from nucleus to ribosome in
the form of genetic code
• tRNA – Acts as adapter molecule ,carries Amino
Acid and drops it to particular location by
recognising codon on mRNA by virtue of having
anticodon.
• rRNA – It makes complex with proteins and form
ribosomal subunits which provide space for
protein synthesis ,single ribosomal RNA of smaller
subunit helps correct orientation of mRNA during
attachment with respect to P and A sites.

21. • snRNA – play significat role in eukayotic mRNA
processing By splicing of exons as snRNPs or snurps
U1,U2, U4,U5 &U6
• scRNA – being component of Signal Recognition
Particle (SRP ) helps in targetting of seceretary
proteins.
• snoRNA – Plays role in gene silencing.
• miRNA – play important role in gene silencing by
blocking mRNA and preventing translation

22. • Si RNA – Plays important role in gene silencing by
interfering transcription.
• gRNA- help in RNA editing in mitochondria , forms
part of editosome and hybridize with matching
sequence of Mrna.
• Catalytic RNA –Ribozymes act as protein enzymes
in catalyzing removal of intron, peptide bond
formation etc.
• aRNA- antisense RNA - is artificially used to block
translation of perticular messenger RNAs so as to
prevent formation of some harmful proteins.

23. • We now turn our attention to RNA, which differs from
DNA in three Respects.
• First, the backbone of RNA contains ribose rather than
2-deoxyribose. That is, ribose has a hydroxyl group at
the2 position.
• Second, RNA contains uracil in place of thymine.
Uracil.
• Third, RNA is usually found as a single poly nucleotide
chain.
• Except for the case of certain viruses, RNA is not the
genetic material and does not need to be capable of
serving as a template for its own replication.

24. • Despite being single-stranded, RNA molecules often
exhibit a great deal of double-helical character.
• This is because RNA chains frequently fold back on
themselves to form base-paired segments between short
stretches of complementary sequences.
• If the two stretches of complementary sequence are near
each other, the RNA may adopt one of various stem-loop
structures in which the intervening RNA is looped out
from the end of the double-helical segment as in a
hairpin, a bulge, or a simple loop.

25. 
Characteristics of RNA.
In an RNA molecule having regions of complementary sequences, the intervening (non-complementary) stretches of RNA
may become “looped out” to form one of the structures illustrated in the figure.
(a) Hairpin (b) Bulge (c) Loop

26. Cont...
• The stability of such stem-loop structures is in some
instances enhanced by the special properties of the
loop.
• For example, a stem-loop with the “tetra loop”
sequence UUCG is unexpectedly stable due to special
base-stacking interactions in the loop.
• Base pairing can also take place between sequences
that are not contiguous to form complex structures
aptly named pseudoknots .
• The regions of base pairing in RNA can be a regular
double helix or they can contain discontinuities, such
as noncomplementary nucleotides that bulge out
from the helix.

27. • RNA splicing is an essential and precisely regulated
post-transcriptional process that occurs prior to
mRNA translation.
• It is thought that at least 70% of the approximately
25,000 genes in the human genome undergo
alternative splicing and that, on average, a given
gene gives rise to 4 alternatively spliced variants -
encoding a total of 90-100,000 proteins which
differ in their sequence and therefore, in their
activities.

28. • A gene is first transcribed into a pre-messenger
RNA (pre-mRNA), a copy of the genomic DNA
containing both introns (destined to be removed
during pre-mRNA processing) and exons (destined
to be retained within the mRNA in order to code
the protein sequence).
• During RNA splicing, exons are either retained in
the mRNA or targeted for removal in different
combinations to create a diverse array of mRNAs
from a single pre-mRNA. This process is known
as alternative RNA splicing.

30. Refrences
• Cell biology , genetics , molecular biology
evolution and ecology
BY : P.S VERMA & V.K AGARWAL
• Genetics by P.K GUPTA
• WWW.RNA images