1. Properties of Nucleic Acids Lecture 1 of Introduction to Molecular Biology 生理所 蔡少正

2. The Discovery of DNA The idea that genetic material is nucleic acid had its roots in the discovery of transformation by Griffith in 1928. In 1944, Avery and colleagues showed chemically that the isolated transforming principle is deoxyribonucleic acid (DNA).

3. The components of DNA A nucleic acid consists of a) nitrogen base, b) pentose, and c) phosphate. Two types of pentose are found in nucleic acids. They distinguish DNA (contains 2- deoxyribose) and RNA (contains ribose).

4. Pyrimidine & Purine Two types of nitrogenous bases: pyrimidine (six- member ring) and purine (fused five-and six-member rings).

5. Building block for nucleic acid A base linked to a sugar is called a nucleoside; when a phosphate group is added, the base-sugar- phosphate is called a nucleotide (building block for nucleic acid). Nucleoside Nucleotide

6. Polynucleotide chain The nucleotides are linked together into a polynucleotide chain by a backbone consisting of an alternating series of sugar and phosphate residues. The terminal nucleotide at one end of the chain has a free 5' group; the terminal nucleotide at the other end has a free 3' group. Traditionally, we write nucleic acid sequences in the 5' to 3' direction, i.e. 5' terminus at the left and 3' terminus at the right.

8. Abbreviations Bases, nucleosomes, and nucleotides have related names. Abbreviations of the form NMP stand for nucleoside monophosphate; "d" indicates the 2-deoxy form.

9. AMP, ADP, and ATP ADP ATP Adenosine

10. Secondary Structure of Nucleic Acid

11. Double Strand DNA Watson and Crick proposed that the two polynucleotide chains in the double helix associate by hydrogen bonding between the nitrogenous bases. In their usual forms, G can hydrogen bond specifically only with C, while A can bond specifically only with T.

12. Complementary bases These reactions are described as base pairing, and the paired bases (G with C, or A with T) are said to be complementary. The two polynucleotide chains run in opposite directions (antiparallel); therefore, one strand runs in the 5'-3' direction, while its partner runs 3'-5'.

13. DNA Denatured DNA can be denatured and renatured. The mid point of the temperature range over which the strands of DNA separate is called the melting temperature (Tm). Tm depends on the proportion of G C base pair (GC content).

14. Forms of DNA DNA can exist in several types of structure families. Rotation per base pair is indicated as (+) for a right- handed duplex and (-) for a left handed duplex. TypeBase/TurnLength/turnDistance /2 basesRotation BB103.4 nm0.34 nm+ A112.3 nm0.21 nm+ ZZ124.5 nm0.33 nm-

15. B DNA

16. B form vs. Z form DNA

17. A Nucleotide

18.  helix conformation Right-handed Left-handed

19. Base-pairing