DNA structure and gene expression Chapter 1 DNA structure and gene expression 1. The building blocks and chemical bonds of DNA, RNA & polypeptides - Covalent bonds provide stability for nucleic acid and proteins while noncovalent bonds (e.g. H-bonds) are very important in allowing the annealing and separation of DNA-DNA, DNA-RNA and protein-protein molecules.

2. DNA structure and replication: - DNA is antiparallel double helix - DNA and RNA display intramolecular hydrogen bonding

- DNA replication is semiconservative. - At the replication fork one newly synthesized strand is continuous while the other newly synthesized strand is discontinuous

3. RNA transcription: - The flow of genetic material DNA -----> RNA -----> protein <-----

- For any one gene, the DNA strand that is used by RNA polymerase as a template is known as the antisense strand while the complementary DNA strand for this gene is known as the sense strrand. - The DNA sense strand has the same sequence as the RNA transcript except that T is replaced by U

- Transcription in eukaryotes requires the interaction between cis-acting elements (DNA promoters and other regulatory sequences) and trans-acting factors (regulatory DNA binding proteins)

4. RNA processing

5. Translation and postranslational modification