DNA 분자구조의 중요성 DNA : 유전 정보가 저장된 물질 Hereditary information is encoded in DNA. 유전 정보 발현의 중심 - DNA directs the development of biochemical, anatomical, physiological, and (to some extent) behavioral traits.

DNA 유전물질 이론의 역사 T. H. Morgan’s group in 1925 : Gene 은 chromosomes 에 있다. → DNA and protein became candidates for the genetic material F. Griffith in 1928 : Transformation 현상 관찰 ( 물질유입에 의한 phenotype 변화 ) Oswald Avery in 1944 : Transforming substance was DNA. → The role of DNA in heredity was first discovered by studying bacteria and the viruses that infect them. Erwin Chargaff in 1950 : 생물 종마다 DNA composition 다르다. → DNA 에는 ( 유전물질로서 필요한 ) 다형성이 존재함. * Chargaff’s rules: 염기 A 와 T 의 수가 같고, G 와 C 의 수가 같다. A. Hershey and M. Chase in 1952 : T2 phage 가 E. coli 감염시킬 때 phage 를 이루는 두가지 물질 (DNA or protein) 중 DNA 만 E. coli cell 에 들어간다.

DNA 구조 규명 Maurice Wilkins and Rosalind Franklin: X-ray crystallography 사용 J. Watson and F. Crick: Models of a double helix J. Watson deduced (based on the images) : Helical structure; the width of the helix and the spacing of the nitrogenous bases; two-stranded nature

Purine + purine: too wide Purine + pyrimidine: consistent with X-ray data DNA 구조 규명 (How its structure accounts for its role) R. Franklin: Antiparallel sugar-phosphate backbones, nitrogenous bases paired in the molecule’s interior J. Watson and F. Crick: A paired only with T and G paired only with C (* Explains Chargaff’s rules) Cytosine (C) Adenine (A) Thymine (T) Guanine (G) Pyrimidine + pyrimidine: too narrow

DNA 구조 - Single strand Sugar-phosphate backbone: 5’-end phosphate 3’-end hydroxyl phosphodiester links Nitrogenous bases Polymer of nucleotides: Nucleotide = Deoxyribose + base + phosphate Sugar–phosphate backbone Nitrogenous bases Thymine (T) Adenine (A) Cytosine (C) Guanine (G) DNA nucleotide Sugar (deoxyribose) 3 end Phosphate 5 end

DNA 구조 - Double helix Antiparallel & Complementary, Radius = 1nm, 0.34 nm/nucleotide, 10 nt/turn, A-T pair: 2 hydrogen bonds, G-C pair: 3 hydrogen bonds Hydrogen bond 3 end 5 end 3.4 nm 0.34 nm 3 end 5 end 1 nm