文档介绍：Chapter 1 (Section C)
The Structure and Properties of Nucleic Acid
Bases (碱基)
Nucleosides (核苷)
Nucleotides (核苷酸)
Three conceptions need to be differentiated
Bicyclic purines
Monocyclic Pyrimidine
Bases (碱基)
Glycosidic bond
(糖苷键)
R
Ribose or
2’-deoxyribose
Nucleosides (核苷)
In nucleic acids, the bases are covalently(共价) attached to the 1’ position of a pentose sugar ring(戊糖), to form a nucleoside.
Adenosine, guanosine, cytidine, thymidine, uridine
腺苷鸟苷胞苷胸苷尿苷
A nucleotide is a nucleoside with one or more phosphate groups bound covalently to the 3’-, 5’, or ( in ribonucleotides only) the 2’-position. In the case of 5’-position, up to three phosphates may be attached.
Deoxynucleotides
(containing deoxyribose)
Ribonucleotides
(containing ribose)
Phosphodiester bonds
Nucleotides (核苷酸)
Primary sequence:
5’end: not always has attached phosphate groups
3’ end: free hydroxyl
(-OH) group
Phosphodiester bonds (磷酸二酯键)
& primary sequence
Nucleic acid are highly negative charged polymers.
DNA double helix
Watson and Crick , 1953
The ic material of anisms except for some viruses
The foundation of the molecular biology
5’
3’
3’
5’
DNA double helix
DNA double helix
Two separate strands Antiparellel(反向平行)(5’3’ direction)
Complementary (sequence)
Base pairing: hydrogen bonding that holds two strands together (They are essential for replicating DNA and transcribing RNA)
Sugar-phosphate backbones (骨架)(negatively charged): outside
Planar(平面) bases (stack one above the other): inside
Base pairing via hydrogen bonds
A:T
G:C