2. Nucleic acid are long chain polymers of
nucleotides present in nuclei of cell, so
they are also called polynucleotide. They
play an important role in transmission of
hereditary characteristics and biosynthesis
of proteins.
These are the largest and the most complex
organic molecules.
3. Frederic Miesher a swiss
scientist in 1869, isolated
an acidic compound from
the nuclear material of
SALMON sperms, and
named it as NUCLIEN
which is now called
NUCLEIC ACID.
6. The sugar in nucleotide, and so in
nucleic acids , is a PENTOSE. In RNA
and its nucleotide the sugar is RIBOSE,
whereas in DNA and its nucleotide it is
DEOXYRIBOSE. The prefix deoxy -
means “without oxygen” .
Nucleotides can be hydrolyzed to yield
nucleosides and phosphoric acid.
11. 11
C
C
C
C
N
N
O
N
C
C
C
C
N
N
O
N
N
N
C
Hydrogen Bonds
The bases attract each
other because of
hydrogen bonds.
Hydrogen bonds are weak
but there are millions and
millions of them in a
single molecule of DNA.
The bonds between
cytosine and guanine are
shown here with dotted
lines
12. 12
Hydrogen Bonds, cont.
When making
hydrogen bonds,
cytosine always
pairs up with
guanine
Adenine always
pairs up with
thymine
Adenine is bonded
to thymine here
C
C
C
C
N
N
O
O
C
14. Nucleosides
Pyrimidine Purine
Nucleoside: a compound that consists of D-ribose or 2-deoxy-D-
ribose (monosaccharide) covalently bonded to a nucleobase by
a -N-glycosidic bond
Covalent linkage forms between N9 of purines or N1 of
pyrimidines to C1 (anomeric carbon of ribose or 2-deoxyribose)
16. Monomers
nucleotides, are made up of three parts:
(a) Phosphate (phosphoric acid)
(b) N-base (Nitrogenous base)
(c) Sugar ~ ribose or deoxyribose
24. DNA consists of two molecules that are
arranged into a ladder-like structure called
a Double Helix.
A molecule of DNA is made up of millions
of tiny subunits called Nucleotides.
26. • 1° structure: the order of bases on the
polynucleotide sequence; the order of bases
specifies the genetic code
• 2° structure: the three-dimensional conformation
of the polynucleotide backbone = double helix
structure
• 3° structure: supercoiling
• 4° structure: interaction between DNA and
proteins
29. Four stranded form of DNA (quadruplex
DNA)
Role in regulating and stabilizing
telomeres and in regulation of gene
expression
Small molecules such as porphyrins
and anthraquinones present, to
stabilize the structure
30.
31. Structural features of A-, B-, and Z- DNA
Type A-DNA B-DNA Z-DNA
Helical sensesright handed right handed left handed
Diameter (Å) ~26 ~20 ~18
Base pairs/turn 11 10 12
Major groove narrow/deep wide/deep Flat
Minor groove wide/shallow narrow/deep narrow/deep
32.
33.
34. Properties of Nucleic Acids:
• Nucleic acids are insoluble in alcohol, slightly soluble
in cold water, but readily dissolved in hot water and
dilute alkalies, forming alkali salts. They are
precipitated by HCL and by excess of acetic acid.
• Feulgen Test differentiates the DNA from RNA, if the
deoxyribose sugar is present, a red color is produced
with the dye. Ribose sugar do not exhibit this reaction.
Hydrolysis of nucleic acids gives nucleotide,
which can be considered the units that make
up the polymer.
35. Biological Functions of Nucleic Acid
DNA is the chemical basis of heredity and may be
regarded as the reserve of genetic information.
The proteins are synthesized by various RNA molecules
in the cell but the message for the synthesis of a
particular protein is present in DNA.
DNA is exclusively responsible for maintaining the
identity of different species of organisms over millions of
years.
