BIO 3110 Study Guide - Midterm Guide: Serratia Marcescens, Micrococcus Luteus, Pyrimidine Dimer
Document Summary
Purpose: to determine the mutagenic and lethal effects of uv light on bacteria. Uv range (250-400 nm) can damage bacteria. Principle effect on bacteria mutations (mistakes in the dna code of the cell: thymine dimers. Two adjacent thymine bases become linked to one another instead of pairing to the adenine bases across the dna helix. Major effect of these thymine dimers is the blockage of dna replication at the dimer itself. Replication can resume beyond the dimer which will leave a gap in the new. Transcription is also stopped at the dimer which stops the expression of genes located downstream from the dimer. Uv light is often used as a bacteriocidal agent for keeping contamination low. Bacteria also have structures that reduce the effects of exposure to light: carotene pigments: found in staphlyococcus and micrococcus confer a degree of uv resistance and help prevent a related problem called photooxidation.
