2. DNA
Deoxyribonucleic acid, a self replicating material
which is present in nearly all living organisms as
the main constituent of chromosomes.
It is the carrier of genetic information.
Most DNA is located in the cell nucleus where is
it called nuclear DNA, but a small amount of DNA
can also be found in the mitochondrial it is called
mtDNA.
3.
4. STRUCTURE OF DNA
• DNA has three main components.
i. Deoxyribose (Pentose sugar)
ii. Base (Nitrogen base pairs)
iii. Phosphate group
5. Deoxyribose
• A sugar derived from ribose by replacement of
a hydroxyl group by hydrogen.
• Role of deoxyribose:
The nucleic acid DNA is built of nucleotides
with a deoxyribose sugar.
6.
7. BASES
• A nitrogenous base is simply a nitrogen
containing molecules that has the same chemical
properties as a base.
• They are the particularly important since they
make up the building blocks of DNA.
• Four bases are present in DNA(A,G,T,C).
• They are classified into two division
I. Pyrimidine
II. Purine
8. • Pyrimidine made of one 6 members ring.
• Purine made of 6member ring fused to a 5
member ring.
9. PHOSPHATE
• DNA are made of nucleotides.
• When it gets joined to the growing strand of
DNA , two of its phosphates are lost, and the
remaining one attaches to another
nucleotides sugar.
• 5’ end always has the phosphate attached.
11. DOUBLE HELIX DNA
• The discovery in 1953 of the double helix, the
twisted ladder structure of deoxyribonucleic
acid by James watson and Crick.
How double helix structure maintained?
• Sugar – phosphate backbone is hydrophilic so
is position on the outside.
• Nitrogenous bases are very reactive so are
protected on inside.
• Polynucleotide's are antiparallel, they run in
opposite directions.
12.
13. DOUBLE HELIX AND HYDROGEN
BONDING
• Made of two strands of nucleotides that are
joined together by hydrogen bonding.
• Adenine and thymine are pair up and cytosine
and guanine are pair up.
• Each pair is connected through hydrogen
bonding.
• Hydrogen bonding always occurs between one
pyrimiding and one purine.
14.
15.
16. TYPES AND CONFORMATIONS OF DNA
B-DNA:
• DNA duplex model proposed by watson and
crick is right handed spiral and is called B-DNA
(Balanced DNA).
• It is more hydrated and most frequently found
DNA in living cells.
• Single turn of helix has 10 base pairs.
• It is physiologically and biologically active
forms. And it can changed into other forms.
17. A-DNA:
• Another right handed duplex model is A-DNA
(Alternate DNA).
• Here a single turn of helix has 11 base pairs.
• Right handed DNA is known to change
temporarily into the left handed form at least
for a short distance.
• Such changes may cause in gene expressions .
18. Z-DNA:
• Z-DNA(zigzag DNA) is left handed double helix
with zigzag backbone alternate purine and
pyrimidine bases.
• Single turn of 45Å length with 12 base pairs
and single groove.
19.
20.
21. RNA
• Ribonucleic acid, a nucleic acid present in all
living cells.
• It is principal role is to act as a messenger
carrying instructions from DNA for controlling
the synthesis of proteins , although n some
viruses RNA rather than DNA carries the
genetic information.
• RNA is a polymer of ribonucleotieds linked
together by 3’-5’ phosphodiester linkage.
22.
23. PRIMARY STRUCTURE OF RNA
• Like DNA, each RNA strand has the same basic
structure, composed of nitrogenous bases
covalently bound to a sugar-phosphate
backbone.
• However, unlike DNA, RNA is usually a single-
stranded molecule.
24.
25. TYPES OF RNA
• In all prokaryotic and eukaryotic organisms,
three main classes of RNA molecules exit.
i. Messenger RNA (mRNA)
ii. Transfer RNA (tRNA)
iii. Ribosomal RNA (rRNA)
26.
27. STRUCTURAL CHARACTERISTICS OF m-
RNA
• The 3’ end of most m-RNA have a polymer of
Adenylate residues (20-250)
• The tail prevents the attack by 3’ exonucleases
• Histones and interferons do not contain poly A
tails.
• The m-RNA molecules are formed with the help of
DNA template during the process of transcription.
28. • The sequence of nucleotides in mRNA is
complementary to the sequence of
nucleotides on template DNA.
• The sequence carried on m-RNA is read in the
form of codons.
• A codon is made up of 3 nucleotides.
• The m-RNA is formed after processing of
heterogeneous nuclear RNA.
29.
30.
31. RIBOSOMAL RNA(r-RNA)
• The eukaryotes ribosome contain two major
nucleoprotein subunits.
• A large one with a molecular weight(60s) and
smaller subunit with a molecular weight(40s).
• The 60s subunits contain a 5s ribosomal RNA,
5.8s rRNA, and a 28s rRNA; there are also
probably more than 50 specific polypeptides.
• The 40s subunits smaller and contains a single
18s rRNA and approximately 30 distinct
polypeptide chains.
32.
33. TRANSFER RNA(tRNA)
• Transfer RNA are the smallest of three major
species of RNA molecules.
• They have 74-95 nucleotide residues.
• They are synthesized by the nuclear
processing of a precursor molecules.
• They transfer the amino acid from cytoplasm
to the protein synthesizing machinery, hence
the name tRNA.
• They are easily soluble, hence called “Soluble
RNA or sRNA.
34. • They are also called adaptor molecules.
• They are at least 20 species of tRNA one
corresponding to each of the 20 amino acid
required for protein synthesis.
37. PRIMARY STRUCTURE OF tRNA
• Linear sequence of nucleotides is 60-90 in
nucleotides long but most commonly 76.
• Many modified bases, sometimes accounting
for 20% of the total bases in any one tRNA
molecules.
• All of them are created post transcriptioally.
38.
39. SECONDARY STRUCTURE OF tRNA
• 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 in a
consistent feature.
40. • All tRNA contain 5 main arms or loops which
areas follows:
i. Acceptor arm
ii. Anticodan arm
iii. D HU arm
iv. T Ψ C arm
v. Extra arm
41. TERTIARY STRUCTURE OF t-RNA
• The L-shaped tertiary structure is formed by
further folding of the clover leaf due to
hydrogen bonds between T and D arms.
