Sasna.p.s

1.RIGHT HANDED DOUBLE HELIX WITH

SHORTER AND MORE COMPACT HELICAL

STRUCTURE[wider and less flexible].

2.CONDITION: 75% OF RELATIVE HUMIDITY &

na+,k+,cs+ ions.

3. WHEN THE PUCKERING OF THE RIBOSE

UNIT CONCERNED C3 IS OUT OF THE PLANE

SO IT IS C3 ENDOPUCKERING

4. HELIX DIAMETER :25.5 A*

5.RISE PER BASE PAIR :2.3A*

6.BASE PAIRS PER TURN OF HELIX :11

7:HELICAL PITCH :25.30A*

8.A DNA IS WIDER,LESS FLEXIBLE THAN B DNA IT CAN INCORPORATE MORE BASE PAIRS PER HELICAL TURN

9.PRESENCE OF MAJOR AND MINOR GROOVES.BUT SLIGHT INCREASE IN THE NUMBER OF BASE PAIR;RESULTING TIGHTER ROTATION ANGLE.AND SMALL RISE PER TURN.SO MAJOR GROOVE IS NARROW AND VERY DEEP. MINOR GROOVE IS VERY BROAD AND SHALLOW

1.THE TWO CHAIN IN THE DOUBLE HELIX ARE

ANTIPARALLEL [ones goes 5’-3’ where as

complementary strand goes 3’-5’]

2.THE BASES ON THE 2 CHAINS PAIR IN A

COMPLEMENTARY FASHION ADENINE [A] PAIR

WITH THYMINE [T]. GUANINE[G] PAIR WITH

CYTOSINE[C]

3.PHOSPHATE GROUPS ARE LINKED TOGETHER

THE SUGAR BACKBONE HAVE PHOPHODIESTER

BONDS

4. HYDROGEN BONDS BETWEEN

BASES [3 FOR G-C, 2 FOR A-T] HOLD

HELIX TOGETHER

5. THERE ARE 10 BASE PER TURN OF

THE HELIX SO THE HELIX ROTATES 36

DEGREE PER BASE

6. THE RISE OF DOUBLE HELIX IS THE

DISTANCE PARELLEL TO THE AXIS OF

THE HELIX FROM THE LEVEL OF ONE

BASE TO THE LEVEL OF ADJACENT

BASE

7.THE PITCH IN B- DNA IS 3.4 nm BECAUSE

THE RISE IS 0.34 nm AND THERE ARE 10 BASE

PAIRS PER TURN OF HELIX

8.B-DNA IS FORMED AT THE RELATIVE

HUMIDITY 92% IN THE PRESENCE OF LOW ION

STRENGTH

9.B-DNA POSSES MAJOR AND MINOR

GROOVES

1.C-DNA IS FORMED AT THE RELATIVE

HUMIDITY 66% IN THE PRESENCE OF Li+ IONS

2.RIGHT HANDED WITH AN AXIAL RISE OF

3.32A*

3.9.33 BASE PAIRS PER TURNS OF THE HELIX

4.HELIX PITCH IS 30.97A*

5.THE ROTATIONS PER BASE PAIR IS 38.58

DEGREE

6.HELIX DIAMETER IS 19A*

7.MAJOR AND MINOR GROOVE IS ABSENT

1.LEFT HANDED HELICAL ROTATION[RICH,NORDHIEM AND WANG IN 1984]

2.HEXA NUCLEOTIDE

3.CGCGCG FORMS THE DUPLEX OF ANTIPARRELLEL STRAND

4.THE PHOSPHATES IN THE Z DNA BACKBONE IS ZIG-ZAG MANNER HENCE THEY TERMED AS Z-DNA

5. ADJACENT SUGAR RESIDUE HAVE

ALTERNATING ORIENTATION

[REPEATING UNIT IS A DINUCLEOTIDE]

6.Z-DNA HAVE ONLY ONE DEEP

HELICAL GROOVE

7.Z-DNA INVOLVED IN REGULATION

OF GENE EXPRESSION,GENETIC

RECOMBINATION,

8.Z-DNA SERVE AS A RECOGANITION

SIGNALS IN THE REGULATION OF

GENETIC TRANSCRIPTION AND DNA

REPLICATION.IT ALSO PLAY A ROLE

IN GENE CONVERSION AND GENETIC

INSTABILITY

9.Z-DNA IS FORMED AT VERY HIGH

SALTCONCENTRATION

CHARACTERISTIC A-DNA B-DNA C-DNA Z-DNA

CONDITIONS 75% OF

RELATIVE

HUMIDITY;K+

Na+,Cs+ IONS

92% RELATIVE

HUMIDITY ;LOW

ION STRENGTH

60% RELATIVE

HUMIDITY ;Li+

IONS

VERY HIGH SALT

CONCENTRATI-

ON

SHAPE BROADEST INTER MEDIATE NARROW NARROWEST

HELIX SENSE RIGHT

HANDED

RIGHT HANDED RIGHT HANDED LEFT HANDED

HELIX DIAMETER 25.5 A* 23.7 A* 19.0 A* 18.4 A*

RISE PER BASE

PAIR(h)

2.3 A* 3.4 A* 3.32 A* 3.8 A*

BASE PAIRS PER

TURN OF

HELIX(n)

11 10.4 9.33 12(=6 DIMER)

HELIX PITCH(hXn) 25.30 A* 35.36 A* 30.97 A* 45.60 A*

CHARACTERISTICS A DNA B DNA C DNA Z DNA

ROTATION PER

BASE PAIR

+32.72 +34.61 +38.58 -60(PER

DIMER)

BASE PAIR PER TILT 19 DEGREE 1 DEGREE _ 9 DEGREE

GLYCOSIDIC BOND ANTI ANTI _ ANTI FOR

C-T

SYN FOR

A-G

MAJOR GROOVE NARROW

AND VERY

DEEP

WIDE AND QUITE

DEEP

_ FLAT

MINOR GROOVE VERY BROAD

AND

SHALLOW

NARROW AND

QUITE DEEP

_ VERY

NARROW

AND DEEP