structure and function of biologically impt nucleotides.

1. Presented by :
Dr Nainika Sharma
Periodontology first year PG

2.  Frederic Miesher in 1869, isolated an acidic compound
from the nuclear material of SALMON sperms, and named
it as NUCLEIN which is now called NUCLEIC ACID.
 Jones in 1920 proved the fact there are two types of
nucleic acids, i.e., Deoxyribonucleic acid (DNA) and
Ribonucleic acid (RNA).
 In 1935 J. D. Watson and F. H. C Crick, on the basis of
information available not only proposed the “Double
helical” structure of DNA but also suggested what Crick
termed “central dogma of molecular genetics”, which
states that genetic information flows from DNA to RNA to
protein.

4. DNA  RNA  amino acids  proteins

5.  Was trying to develop a vaccination for the
pneumococcus bacteria.
 Vaccine- a prepared substance from killed or
weakened disease causing agents used to
prevent future infections
 He was working with two strains of bacteria.
 Rough - bacteria had a rough appearance in
culture, non-virulent (doesn't kill)
 Smooth - bacteria had a smooth appearance
in culture, virulent (kills)

6. The Genetic Material is DNA – Alfred Hershey
and Martha Chase, 1952
Previously, scientists thought that proteins
were the hereditary molecule
Hershey and Chase worked with viruses that
infect bacteria called bacteriophages
› Through a series of experiments, they were able
to show that DNA, not protein, is the hereditary
molecule.

8. M.H.F. Wilkins and Rosalind Franklin, early
50’s
Wilkins and Franklin studied the structure of DNA
crystals using X-rays.
They found that the crystals contain regularly
repeating subunits.
The X pattern produced by DNA suggested that
DNA contains structures with dimensions of 2 nm,
0.34 nm, and 3.4 nm. The dark structures at the
top and bottom indicate that some structure was
repeated, suggesting a helix.

9. Rosalind Franklin
X-ray diffraction image of DNA

10. James Watson and Francis H.C. Crick, 1953
Watson and Crick used Chargaff's base data and
Franklin’s X-ray diffraction data to construct a model of
DNA.
The model showed that DNA is a double helix with
sugar-phosphate backbones on the outside and the
paired nucleotide bases on the inside, in a structure
that fit the spacing estimates from the X-ray diffraction
data.
Chargaff's rules showed that A = T and G = C, so
there was complementary base pairing of a purine with
a pyrimidine, giving the correct width for the helix.
The paired bases can occur in any order, giving an
overwhelming diversity of sequences.

11. Watson & Crick with their model of DNA

12.  Base pairing rule is A-T and G-C.
 Thymine is replaced by Uracil in RNA.
 Bases are bonded to each other by
Hydrogen bonds.
 Discovered because of the relative percent
of each base; (notice that A-T is similar and
C-G are similar).

13. Erwin Chargaff

14.  The role of RNA in protein synthesis was suspected
already in 1939.
 Severo Ochoa won the 1959 Nobel Prize in Medicine
after he discovered how RNA is synthesized.
 Carl Woese realized RNA can be catalytic in 1967 and
proposed that the earliest forms of life relied on RNA both
to carry genetic information and to catalyze biochemical
reactions—an RNA world.

15.  In 1990 it was found that introduced genes
can silence homologous endogenous genes
in plants, now known to be a result of RNA
interference.
 In same year, the discovery of gene
regulatory RNAs has led to attempts to
develop drugs made of RNA, like siRNA, to
silence genes.

16.  Two types;
 DNA
 RNA
 The building blocks of
nucleic acids are
called
NUCLEOTIDES

17.  Nucleotides:
monomers of nucleic acids.
› All nucleic acids consist of many nucleotides
bonded together.
 Nucleic acids are polynucleotide.
 Their building blocks are nucleotides

18.  nucleotides, are made up of three parts:
(a) Phosphate (phosphoric acid)
(b) N-base (Nitrogenous base)
(c) Sugar ~ ribose or deoxyribose

19. PHOSPHATE SUGAR
Ribose or
Deoxyribose
NUCLEOTIDE
BASE
PURINES PYRIMIDINES
Adenine (A)
Guanine(G)
Cytocine (C)
Thymine (T)
Uracil (U)

20. RIBOSE DEOXYRIBOSE
CH2OH
H
OH
C
C
OH OH
C
O
H HH
C
CH2OH
H
OH
C
C
OH H
C
O
H HH
C

21.  Purines: adenine, guanine (double ring)
 Pyrimidine: thymine, cytosine (single rings)
Adenine :
Thymine :
Guanine : Cytosine :

22. The bases always pair up in the same way
A purine with a pyrimidine
Adenine forms a bond with Thymine
Cytosine bonds with Guanine
Adenine Thymine
Cytosine Guanine

23.  Sugar = Deoxyribose
 Specific Base Pairing
› Adenine-Thymine
› Guanine-Cytosine
 Forms a double Helix Structure

24.  Sugar= Ribose
 Thymine gets
replaced by Uracil
 Single stranded

25. Molecule: DNA RNA
Structure
/shape
Double helix or
α-helix
Linear, single
strand
# of strands 2 1
Sugar Deoxyribose Ribose
N-bases A, T, G, C A, U, G, C
Structural (and functional)
Comparison of DNA & RNA

26.  DNA is used to store genetic information
› It is replicated before cell division.
 DNA is very important so it is stored in the
nucleus.
 It never leaves the nucleus
 Your DNA stores the code for your proteins,
which exhibit your “traits”
 The DNA gets converted to RNA in order to
move out into the cytoplasm

27.  In the cytoplasm it meets up with the
ribosome, where it can synthesize proteins
 Stores genetic information.
 Maintains growth and repair.
 Controls all cellular activities.
 Contains protein codes.
 Ensures each daughter cell & gamete
receives exact genetic information.

28.  Abbreviation of deoxyribonucleic acid.
 It is a polymer of Deoxyribo nucleotide.
 This thread like structure is a combination of
large number of nucleotide units joined
together.
 This Polynucleotide contains genetic
information that gives rise to chemical and
physical properties of organisms.

29.  LOCATION:
 It can be found in chromosomes (specifically
nucleus), mitochondria and chloroplast of the
cell.
 It is present in every living organism because
it contains genetic material.
 ISOLATION:
 From viruses, bacteria, thymus gland,
spleen, blood, hair, skin, etc

30.  Size shows great variation.
 Only 1.7µm long in simple structure of
simian virus with 5 or 6 genes. and can also
extend to 2m in Human DNA.
 The size of human DNA inside the
chromosome is just 200 nm.

32.  In fact, the DNA usually consists of a double
strand of nucleotides.
 The sugar-phosphate chains are on the
outside and the strands are held together by
hydrogen bonds between the bases.
 There are grooves in the DNA molecule:
minor groove and major groove, winding
along the molecule parallel to the
phosphodiester backbone.

33. The bases always pair up in the same way
A purine with a pyrimidine
Adenine forms a bond with Thymine
and Cytosine bonds with Guanine
Adenine Thymine
Cytosine Guanine

34. PO4
PO4
PO4
thymine
PO4
PO4
PO4
PO4
adenine
cytosine
PO4
guanine

35.  Two types;
 Circular DNA
 Non-Circular DNA
 CIRCULAR DNA :
 In Eukaryotes: The ends of DNA are
cohesive,so they join forming a circular
DNA.eg.mitochondria,chloroplast,etc.
 In Prokaryotes: mostly it is in the form of
PLASMID whose replication do not depend on
genomic DNA.eg.bacteria.

36.  NON-CIRCULAR DNA:
 The two anti parallel strands of DNA twist
around each other to form helical structure of
double helix.

38. 1) DNA must unwind and break the hydrogen
bonds
2) Each strand is used as a template (blueprint)
3) Two new strands of DNA are formed from
the original strand by the enzyme DNA
Polymerase

39. During replication, an enzyme called
helicase “unzips” the DNA molecule along the
base pairing, straight down the middle.
Another enzyme, called DNA polymerase,
moves along the bases on each of the
unzipped halves and connects complementary
nucleotides.

40. DNA
polymerase
Replication fork
Growth
Growth
New strand
Original strand
DNA polymerase
New strand
Original strand
Replication fork
Nitrogenous bases

41.  Just as DNA polymerase makes new DNA, a similar
enzyme called RNA polymerase makes new RNA.
 RNA polymerase temporarily separates the strands of a
small section of the DNA molecule.
› This exposes some of the bases of the DNA molecule.
 Along one strand, the RNA polymerase binds
complementary RNA nucleotides to the exposed DNA
bases.

42.  As the RNA polymerase moves along, it makes a strand
of messenger RNA (mRNA).
› It is called messenger RNA because it carries DNA’s
message out of the nucleus and into the cytoplasm.
› mRNA is SINGLE STRANDED!
 When the RNA polymerase is done reading the gene in
the DNA, it leaves.
 The separated DNA strands reconnect, ready to be read
again when necessary.
 mRNA moves out of the nucleus and finds a ribosome
 On the ribosome, amino acids are assembled to form
proteins in the process called translation.

43. A C G G T A
TEMPLATE STRAND
T TG C C A
The backbone is made of alternating
sugars and phosphates.
- Remember: Sugar ALWAYS
attaches to the Nitrogen base

45.  Ribonucleic acid usually called as RNA, is a
biologically important type of molecule that
consists of a long chain of nucleotide units.
 It is a single stranded chain of nucleotides that
contains genetic information and it functions for
the synthesis of proteins and also to transfer
genetic information from one generation to the next.

46.  There are three types of RNA in a cell.
 Ribosomal RNA (rRNA)
 Messenger RNA (mRNA)
 Transfer RNA ( tRNA)
• Their main function is to make proteins after
taking instructions from the DNA.
• They are temporarily present in the cell.

47. from to to make up
also called which functions to also called also calledwhich functions to
can be
RNA
Messenger RNA Ribosomal
RNA
Transfer
RNA
mRNA Carry instructions rRNA
Combine
with proteins
tRNA
Bring
amino acids to
ribosome
DNA Ribosome Ribosomes
Which functions to

48.  Also known as mRNA.
 Messenger RNA is a single long chain of
nucleotides
 It is a molecule of RNA encoding a chemical
"blueprint" for a protein product.
 mRNA istranscribed from a DNA template,
and carries coding information to the sites
of protein synthesis: the ribosomes.

49.  In mRNA as in DNA, genetic information
is encoded in the sequence
of nucleotides arranged
into codons consisting of
three bases each.
 Each codon encodes for a specific amino
acid, except the stop codons that
terminate protein synthesis.

50.  It is also known as rRna.
 Ribosomal RNA is the central component of
the ribosome, the protein manufacturing
machinery of all living cells.

51.  Ribosomal RNA has two units,
 one large and
 the other small.
. Large subunit
Small subunit
Ribosomal RNA
(rRNA)

52.  The function of the rRNA is to provide a
mechanism for decoding mRNA into amino
acids and to interact with
the tRNAs during translation.
 The tRNA then brings the necessary amino
acids corresponding to the appropriate
mRNA codon.

53.  Transfer RNA (abbreviated tRNA) is a
small RNA molecule (usually about 74-95
nucleotides) that transfers a specific
active amino acid to a growing polypeptide
chain at the ribosomal site of protein synthesis
during translation.
 act as adapter between nucleotides codons and
amino acids. They pick up free amino acids in
cytoplasm and carry them into the ribosomes
where polypeptide chain is elongated.

54.  Each tRNA carries an amino
acid
 As each codon of the mRNA
molecule moves through the
ribosome, the corresponding
amino acid is brought into the
ribosome by the tRNA.
 Each tRNA molecule has three
unpaired bases
(anticodons)which are
complimentary to mRNA codons

55.  There are 20
different
tRNAs, for the
different
aminoacids.

56.  tRNA carries (or transfers) the correct amino
acid to the codon on the mRNA.
 tRNA has an ANTICODON that can attach to
mRNA’s codon.

57.  mRNA is sandwiched between the small and
large subunits and the ribosome catalyzes the
formation of a peptide bond between the 2
amino acids that are contained in the rRNA.
 The ribosome also has 3 binding sites called A,
P, and E.
 The A site in the ribosome binds to an
aminoacyl-tRNA (a tRNA bound to an amino
acid).

58.  The amino (NH2) group of the aminoacyl-tRNA,
which contains the new amino acid, attacks the
ester linkage of peptidyl-tRNA (contained within
the P site), which contains the last amino acid of
the growing chain, forming a new peptide bond.
 The tRNA that was holding on the last amino
acid is moved to the E site, and what used to be
the aminoacyl-tRNA is now the peptidyl-tRNA.
 A single mRNA can be translated
simultaneously by multiple ribosomes.

59. Translation- the Ultimate Goal!
•Going from mRNA to the final product

60.  How does DNA (a twisted latter of atoms)
control everything in a cell and ultimately an
organism?
› DNA controls the manufacture of all cellular proteins
including enzymes
› A gene is a region of DNA that contains the
instructions for the manufacture of on particular
polypeptide chain (chain of amino acids)
DNA is a set of blueprints
or code from making proteins

61. Where is the DNA?
Protein synthesis –
the manufacture of
proteins
Where are proteins
made in the cell?

62.  mRNA combines with a ribosome and tRNA and
makes a protein
 Remember:
› mRNA carries the codon (three base sequence that
codes for an amino acid)
› tRNA carries the anticodon which pairs up with the
codon
› tRNA brings the correct amino acid by reading the
genetic code

63. GUA UCU GUU ACC GUA
mRNA
•mRNA carries the same message as DNA but
rewritten with different nitrogen bases.
•This message codes for a specific sequence of
amino acids
•Review..Amino acids are the building blocks of…
•PROTEINS

64. GUA UCU GUU ACC GUA
mRNA
•Codon: a sequence of 3 nitrogen bases on
mRNA that code for 1 amino acid
•It’s a TRIPLET code

65. GUA UCU GUU ACC GUA
mRNA
•These codons are universal for every
bacteria, plant and animal on earth
•There are 64 codons which code for all 20
amino acids on earth.

66. GUA UCU GUU ACC GUA
mRNA
•The mRNA molecule travels to the
ribosomes where the mRNA codes are
“read” by the ribosomes
•Ribosomes hold the mRNA so another type
of RNA, transfer RNA (tRNA) can attach to
the mRNA
Ribosome

67. GUA UCU GUU ACC GUA
mRNA
RibosomeCAU AGA

69.  Amino acids link
together to form a
protein
 The new protein
could become cell
part, an enzyme, a
hormone etc.

70.  Say the mRNA strand reads:
› mRNA (codon) AUG–GAC–CAG-UGA
› tRNA (anticodon) UAC-CUG-GUC-ACU
 tRNA would bring the amino acids:
 Methionine-Aspartic acid-Glutamine-stop

71. 1)mRNA is transcribed in the nucleus and leaves
the nucleus to the cytoplasm.
2) mRNA attaches to the ribosome.
3)The codon on the mRNA is read by the
anticodon on the tRNA.
4) tRNA brings the amino acid as it reads mRNA.
5) The amino acids are joined together to form a
polypeptide (protein).
6) When a stop codon is reached (UAA, UAG,
UGA) protein synthesis stops.

73.  A probe is a molecule with a strong affinity
for a specific target, which can be easily
detected after its interaction with the target.
 Specificity depends based on the interaction
between complementary polynncleotide
strand.
 Probes obtained by amplification of naturally
occurring DNA sequence or chemical
synthesis.

74.  DNA based technique is used in
 Genetic diseases
 Cancers
 Slow growing / difficult isolation bacterial
infections

75.  Telomerase activity maintain appropriate
length of the telomer sequences of
chromosome.
 This activity is absent in most somatic cells
leads to decrease in the telomer repeating
and substantial reduction of the telomer.
 Telomer length appears to serve as a mitotic
clock that limit the replication potential of
mammalian cells.

76.  Genetic material is rearranged by
breaking and joining portion of the same
DNA molecule or portion of different DNA
molecule.
 Recombination takes place between DNA
of different organism to generate new
composite DNA.

77.  DNA Recombination technology used for
 Antibodies
 Proteins
 Production of more disease resistance in
organisms

78.  DNA can be collected from hair, tooth, blood,
saliva, sweat, semen, urine, bone, tissues
and cellular contents.
 After extracting DNA from various method
and used for
 Gender identification
 Personal identification
 Parental disputes, etc.

79.  Nucleic acids are the multicoded complex
molecule in the biological system from
virus to humans.
 Exploring the nature, properties, possible
to understand the molecules and to bring
the desirable modification in the future
world for the benefits of living system.

80.  Text Book Of Medical Biochemistry, MN Chatterjea, Rana Shinde,
3rd Edition.
 Text Book Of Biochemistry, U. Satyanarayana, 2nd Edition.
 Text Book Of Biochemistry With Clinical Correlations, Thomas M.
Devlin, 4th Edition.
 Role of DNA in forensic odontolgy, Shruthi Nayak et.al, KSDJ vol-
31:no-01;jan-march 2012.
 Harper 29 th edition …pg.336 to 352