The primary structure of nucleic acids is the covalent structure and nucleotide sequence.
The secondary structure of nucleic acids is the regular stable structure taken up by some or all the nucleotides.
The tertiary structure of nucleic acids is the complex folding of large chromosomes or the elaborate folding of tRNA and rRNA structures.
X ray diffraction patterns revealed DNA molecules are helical.
Offset pairing of the two strands creates a major and minor groove.
Major grooves expose more the nucleotides the to environment.
Minor grooves expose less of the nucleotides to the environment.
There are three hydrogen bonds between G and C.
There are two hydrogen bonds between A and T.
Parallel arrangement is when 3', 5' phosphodiester bonds run in the same direction.
Antiparrallel arrangement is when 3', 5' phosphodiester bonds run in the opposite direction.
The antiparrallel arrangement of DNA was confirmed by x ray analysis.
The offset pairing of the two strands creates a major groove and a minor groove on the surface of the duplex.
The double helix has 10.5 base pairs per helical turn and is about 36 A long.
Double helix DNA strands are complementary.
When adenine occurs on one chain, thymine is found in the other.
When guanine occurs in one chain, cytosine is found in the other.
Hydrogen bonding does not contribute significantly to stability of the structure.
The double helix is stabilized by the metal cations that shield the negative charges of the backbone phosphates and the base stacking interactions between successive base pairs.
Successive guanine cytosine hydrogen bonds are stronger than successive adenine thymine hydrogen bonds.
Duplexes with a higher guanine cytosine content are more stable.
Pyrimidines and purines are aromatic
Step one of DNA replication is the preexisting parent strands become separated.
Step two of DNA replication is each parent strand serves as a template for the biosynthesis of a complementary daughter strand.
Structural variation in DNA reflects different possible conformations of deoxyribose, rotation about the contiguous bonds making up the phosphodeoxyribose backbone, and free rotation about the C1'-N-glycosyl bond.
The B form of DNA is the Watson Crick structure.
The B form of DNA is the most stable for a random sequence DNA molecule under physiological conditions.
The A form of DNA is a right handed double helix with a wider helix, 11 base pairs per turn, and a tilted plane.
The A form is favored in situations devoid of water.
The Z form of DNA is a left handed helix with 12 base pairs per turn and a backbone with a zig zag appearance.
The Z form of DNA appears more slender and elongated.
Diagram
A) A form
B) B form
C) Z form
D) B form
E) A form
F) Z form
G) A form
H) B form
I) Z form
The helical sense in A form is right handed, B form is right handed, and Z form is left handed.
The diameter of A form is 26A, B form is 20A, and Z form is 18A.
The base pairs per turn in A form is 11, B form is 10.5, and Z form is 12.
The helix rise per base pair in A form is 2.6A, B form is 3.4A, and Z form is 3.7A.
The base tilt normal to the helix axis in A form is 20, B form is 6 and Z form is 7.
The sugar pucker conformation in A form is C-3' endo, B form is C-2' endo, and Z form is C-2' endo for pyrimidines and C-3' endo for purines.
The glycosyl bond conformation in A form is anti, B form is anti, and Z form is anti for pyrimidines and syn for purines.
A palindrome is a region of the DNA that is identical when read either forward or backward. This is applied to regions of DNA with invertedrepeats.