RNA

ACTIVE FIGURE 28. 10 General features of a replication fork ACTIVE FIGURE 28.10 General features of a replication fork. The DNA duplex is unwound by the action of DNA gyrase and helicase, and the single strands are coated with SSB (ssDNA-binding protein). Primase periodically primes synthesis on the lagging strand. Each half of the dimeric replicative polymerase is a “core” polymerase bound to its template strand by a -subunit sliding clamp. DNA polymerase I and DNA ligase act downstream on the lagging strand to remove RNA primers, replace them with DNA, and ligate the Okazaki fragments. Test yourself on the concepts in this figure at http://chemistry.brookscole. com/ggb3 Fig. 28-10, p. 907

Nucleotide Excision Repair -A generic example of how damage such as pyrimidine dimers are repaired