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Deoxyribonucleic acid (DNA), DNA, image - Coggle Diagram
Deoxyribonucleic acid (DNA)
The set of DNA molecules that contains all genetic information for an organism is called genome
DNA is most founded in
nuclei of eukaryotic cells
the nucleoid of bacteria
DNA is composed of two long polymer strands
sugar 2-deoxyribose
Phosphate
purine
pyrimide
bases
Back bone of each strand
alternating 2-deoxyribose and phosphate
linked together through phosphodiester
DNA strand has directionality
The four bases found in DNA
adenine (A)
thymine (T)
guanine (G)
cytosine (C)
Structure
DNA can be single handed or aligned to form 2-4 stranded structures
the two strads wrap around each other to form a double helix
double helical structure was first proposed in 1953 by J.D. Watson and F. H. C. Crick
the two strands are held together by base
pairing and antipararel
The most common form of DNA is the B-form
Right-handed conformation
10 bases per turn
each base pair is simililar to the neighboring base pair
a dried DNA fiber produces a type A pattern
Hydrated DNA produces a B-type patter
in which the bases are perpendicular to the helix axis
in which the base pairs are tilted somewhat away from the helix axis
Left-handed conformation (Z-DNA)
DNA can aslo form a left- handed double helix
same hydrogen bonding between the bases
discovered by solving the structure of crystals of short DNA fragments
a solid line drawn between the phosphates in the left -handed conformation
called Z-DNA
in contrast to B-DNA it has has only one deep helical groove
both forms of DNA have two sugar-phosphatebackbones
conformational changes
DNA is normally subjected to a torsional strain that tends to unwind the double helix
torsional strain tends to untwist right-handed B-DNA
right-handed B-DNA to left-handed Z-DNA
changes in the relationship of the bases to the sugar backbone
Every other base in Z-DNA is
rotated about the bond connecting it to the sugar
Function
Replication
Each of the two strands of a DNA double helix contains all of the information necessary to make a new double-stranded molecule.
