This presentation ppt have basic information about RNA and its nature, types and structure

1. 11

2. By
VIRENDRA SINGH SHEKHAWAT
M.SC. (AGRI)

3. 
 Nucleic acids were first isolated by Miescher (1868) from the nuclei
of white blood cells (WBC) of pus.
 A nucleic acid is a macromolecule composed of chains of monomeric
nucleotides.
 Each nucleotide consists of three components: a nitrogenous
heterocyclic base, which is either a purine or a pyrimidine; a pentose
sugar; and a phosphate group.
 Nucleic acids are universal in living things, as they are found in all
cells and viruses.
 Nucleic acids were first discovered by Friedrich Miescher in 1871.
 Nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic
acid (RNA).
NUCLEIC ACID: AN
INTRODUCTION

4. 
The phosphodiester bonds link the 3' carbon in the
sugar ring of one nucleotide to the 5' carbon on the
next nucleotide
The Structure of Nucleic Acids

5. 
Sequence of bases constitutes the genetic
information

6. 
 A nucleic acid that carries the
genetic message from DNA to
ribosomes and is involved in
the process of protein
synthesis is referred to as
RNA(Ribose Nucleic Acid).
 Ribonucleic acid is one of the
two types of nucleic acids
found in all cells.
RNA(RIBOSE NUCLEIC
ACID)

7. 
RNA is similar to DNA but containing ribose in
place of deoxyribose and uracil in place of
thymine.
RNA is a nucleic acid polymer consisting of
nucleotide monomers that acts as a messenger
between DNA and ribosomes and is also
responsible for making proteins out of amino
acids.
Some viruses use RNA instead of DNA as their
genetic material.
CONT……

8.  Location: - In eukaryotes, RNA is found both in nucleus
and cytoplasm. In the nucleus it is a components of
chromosomes, whereas in cytoplasm it is found in
ribosomes. In prokaryotes, it is found in the cytoplasm.
 Synthesis: - The RNA synthesis takes place in the nucleus
on a DNA template. After synthesis it moves from nucleus
to cytoplasm. Thus, RNA usually does no have self
duplication property. In certain viruses like TMV and
plantago virus RNA can synthesize another RNA
molecule.
 Size: - RNA molecule is much smaller in size than DNA.
It consists upto 12,000 nucleotides whereas DNA consists
upto 4.3 million nucleotides.
Main features of RNA

9.  Types: - There are different forms of RNA such as:-
i. messenger RNA (mRNA),
ii. ribosomal RNA (rRNA),
iii. transfer RNA (tRNA) or soluble RNA (sRNA),
Ribosomal and transfer RNAs constitutes about 98% of the
total RNA. All three forms of RNA are synthesized on DNA
template.
 Functions: - In most of the organisms, the usual function
of RNA is transfer of genetic message from nucleus to the
cytoplasm and synthesis of protein in ribosomes. In some
viruses, RNA acts as the genetic material and regulates the
gene action.
CONT……

10. 
 RNA like DNA is a polynucleotide. RNA is either
single stranded or double stranded but not helical
like DNA.
 RNA nucleotides have ribose sugar, which
participate in the formation of sugar phosphate
backbone of RNA.
 The nitrogen base in RNA are: Adenine (A), Guanine
(G), Cytosine (C) and Uracil (U). Thymine is absent
and is replaced by Uracil. Usually RNA is a single
stranded structure.
STRUCTURE OF RNA

11. 
CONT…..
•RNA does not
form an
analogous
double helical
structure.
•RNA form a
heteromeric
double helix.

12. 
CONT….
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

13. 
 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.
CONT…

14. 
Pyrimidines
i. In RNA, pyrimidines bases are of two types, viz.
cytosine and uracil.
ii. These are single ring structures.
iii. They occupy less space in RNA structure.
iv. Pyrimidine is linked with ribose sugar at position 3.
Purines
i. They are same as in DNA i.e. adenine and guanine.
ii. They are double ring compounds.
iii. They occupy more space in RNA structure.
iv. Ribose sugar is linked at postion 9 of purine.
NITROGEN BASES

15. 
…Nitrogen bases…

16.  RNA contains ribose sugar
which is pentose sugar
having five carbon atoms.
 The four carbon atoms are
inside the ring and the fifth
one is with CH2 group.
 This has four OH groups on
1,2,3 and 5 carbon positions.
 Hydrogen atoms are attached
to carbon atoms one to four.
 The ribose sugar has OH
group on carbon atom 2,
whereas DNA has H group.
Ribose sugar

17. 
The phosphate molecule is arranged in
an alternate manner to ribose sugar.
Thus, there is ribose sugar on both
sides of phosphate.
The phosphate is joined with carbon
atom 3 of ribose at one side and with
carbon atom 5 of ribose on the other
side.
Phosphate

18.  Nucleoside = Ribose sugar +
Nitrogen bases
 Nucleotide = Nucleoside +
Phosphate.
 Thus, a nucleotide is a nucleoside
with one or more phosphate
groups covalently attached to it.
 The four different nucleosides of
RNA are ribose adenosine (rA),
ribose guanosine (rG), ribose
cytosine (rC), and ribose
urosine(rU).
Nucleosides and Nucleotides

19. 
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Messenger RNA (mRNA)
Types of RNA

20. 
It constitutes about 5-10% of the total cellular
RNA.
It is most heterogenous in size and base sequence.
It is a single stranded base for base
complimentary copy of one of the DNA strands of
a gene.
It carries the information from nuclear DNA to
cytoplasm for protein synthesis. It is also known
as template RNA.
The molecular weight of an average molecule of
mRNA is 5,00,000 and its sedimentation
coefficient is 8S.
Messenger RNA (mRNA)

21. 
 It is coded so that every three
nucleotides (a codon) correspond to
one amino acid
 . In eukaryotic cells, once precursor
mRNA (pre-mRNA) has been
transcribed from DNA, it is
processed to mature mRNA
 This removes its introns—non-
coding sections of the pre-mRNA
 The mRNA is then exported from
the nucleus to the cytoplasm, where
it is bound to ribosomes
and translated into its corresponding
protein form with the help of tRNA
CONT…….

22. 
 It is found in ribosome in the
cytoplasm.
 It is the catalytic component of
the ribosomes.
 The size of ribosomes is
expressed in terms of ‘S’ units,
based on the rate of
sedimentation in an
ultracentrifuge.
 It constitutes about 80% of the
total cellular RNA.
 The function of rRNA is binding
of mRNA and tRNA to
ribosomes in the cytoplasm.
Ribosomal RNA (rRNA)

23. 
 It is also known as soluble RNA (sRNA).
 It constitutes about 10-15% of total RNA of the cell.
 It is a class of RNA which is of small size of 3S type
and generally have 70 – 90 nucleotides.
 The longest t – RNA has 87 nucleotides.
 Its main function is to carry various types of amino
acids and attach them to mRNA template for
synthesis of protein.
 It has molecular weight of about 25,000 to 30,000
with sedimentation coefficient of 3.8S.
transfer RNA (t – RNA):

24. 
Cont…

25.  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
Small Nuclear RNAs (snRNAs)

26.  microRNAs, short non-coding RNAs present in all living
organisms, have been shown to regulate the expression of
at least half of all human genes. These single-stranded
RNAs exert their regulatory action by binding messenger
RNAs and preventing their translation into proteins.
Micro RNAs (miRNAs)

27.  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.
Small Interfering RNAs
(siRNAs)

28. 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.
CONT….

29. 
 RNA is synthesized by DNA for the transportation
of genetic information to the protein building
apparatus in the cell.
 RNA also directs the synthesis of new proteins using
the genetic information it has transported.
 mRNA (messenger ribonucleic acid) is used to
transfer genetic information through plasma
membranes
 mRNA – It carries genetic formation of DNA (Gene)
for protein synthesis from nucleus to ribosome in the
form of genetic code.
FUNCTIONS OF RNA

30.  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.
 snRNA – play significat role in eukayotic mRNA
processing by splicing of exons as snRNPs or snurps
U1,U2, U4,U5 &U6.
Cont…

31.  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.
 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.
Cont…

32. 
RNA types and functions
Types of RNAs Primary Function(s)
mRNA - messenger translation (protein synthesis)
regulatory
rRNA - ribosomal translation (protein synthesis) <catalytic>
t-RNA - transfer translation (protein synthesis)
hnRNA - heterogeneous nuclear precursors & intermediates of mature mRNAs
& other RNAs
scRNA - small cytoplasmic signal recognition particle (SRP)
tRNA processing <catalytic>
snRNA- small nuclear
snoRNA - small nucleolar
mRNA processing, poly A addition <catalytic>
rRNA processing/maturation/methylation
regulatory RNAs (siRNA,
miRNA, etc.)
regulation of transcription and translation,

33. 
DIFFERENCE BETWEEN DNAAND
RNA
Sr. No DNA RNA
1. It usually occurs inside nucleus
and some cell organelles.
Very little RNA occurs inside
nucleus. Most of it is found in the
cytoplasm.
2. DNA is the genetic material. RNA is not the genetic material
except in certain viruses. e.g., TNIV,
Reovirus.
3. It is double stranded with the
exception of some viruses.
RNA is single stranded with the
exception of some viruses (e.g.,
double
stranded in Reovirus).
4. DNA shows regular helical
coiling.
There is no regular coiling except in
parts of RNA.
5. DNA forms chromosomes of
similar structures.
rRNA forms ribosomes.

34. 
CONT…
Sr. No DNA RNA
6. DNA contains several million
nucleotides.
Depending upon the type, RNA
contains 10-12000 nucleotides.
7. DNA is of only two types, nuclear
and extra nuclear.
There are at least three types of
RNA-rRNA, mRNA and tRNA
8. It contains deoxyribose sugar. It contains ribose sugar.
9. Nitrogen base thymine occurs in
DNA along with three other-
adenine, cytosine
and guanine.
Thymine is replaced by uracil in
RNA. The other three are adenine,
cytosine
and guanine.
10. Renaturation after melting is
slow.
It is quite fast.
11. Hydrogen bonds are formed
between complementary nitrogen
bases of the
opposite strands of DNA (A : T, C
: G)
Base pairing through hydrogen
bonds occurs only in the coiled
parts.

35. 
Sr. No DNA RNA
12. It replicates to form new DNA
molecules.
It cannot replicate itself except in
RNA-RNA viruses.
13. DNA transcribes genetic
information to RNA.
RNA translates the transcribed
message for forming polypeptides.
14. DNA controls heredity,
evolution, metabolism, structure
and differentiation.
RNA controls only protein synthesis.
15.
Its quantity is fixed for cell.
The quantity of RNA of a cell is
variable.
16. DNA controls metabolism and
genetics including variations.
It only controls metabolism under
instructions from DNA.
17.
Purine and pyrimidine bases are
in equal number.
There is no proportionality between
number of purine and pyrimidine
bases.
18. It can be hydrolyzed by enzyme
DNA-ase.
RNA is hydrolyzed by RNA-ase.
CONT…..

36. 