Lectures II-2, 3

Required Reading: Suggested Questions to Answer: Learning Objectives: Lecture Outline - Overview of Nucleic acids & Molecular Biology;  Nucleic acid structure

I.     Significance of Nucleic acids

The "Central Dogma" of molecular biology:

Genes contain the information that specifies protein sequences

 --> The flow of genetic information is from DNA to RNA to protein

Replication (DNA synthesis) ensures the faithful transmission of genetic information from generation to generation (Fig. 3-14, FOB)

At least two additional processes are required for gene expression (the functional manifestation of genetic information) (Fig. 3-15, FOB):

        1) transcription (RNA synthesis)
        2) translation (protein synthesis)

Nucleic acids play two kinds of role in these processes:


II.  Higher order structure of DNA: the Double Helix

Key features of the double helix: Conformational variability in the double helix (Table 23-1, Figs. 3-9 & 23-2, FOB) III.  Secondary structure: base pairing in ssRNA (or ssDNA): (Fig. 4-8, MCB; 23-23 FOB)

Single-stranded molecules may form:

Important for 3-D structure of tRNA, rRNA, ribozymes, etc

Result from “palindromic” sequences (aka inverted repeats)

Helical regions in RNA are usually A-form and may be imperfect due to:


IV. Helix stability

Non-covalent interactions determine the stability of the double helix

Helix Denaturation (melting) and Renaturation (annealing) (Fig. 23-15, FOB)