01:447:380 Lecture Notes - Lecture 2: Dna Supercoil, Topoisomerase, Chromosome
Document Summary
Instead of a nucleus, a bacterium has a nucleoid region. The dna forms loop domains, each of which is anchored by dna-binding proteins. The dna in each loop domain is supercoiled. In most bacteria topoisomerases negatively supercoil the dna, and nucleoid associated proteins (naps) hold it in the proper configuration. Bacterial dna can be supercoiled in either direction. Most bacteria have a circular dna molecule, which may be in the relaxed or supercoiled configuration. Bacterial chromosomes can be positively or negatively supercoiled. A plasmid is a small, circular piece of dna that replicates independently from the bacterium itself. Plasmids can be replicated, and the copies transferred to another bacterium, by a proces known as conjugation. Plasmids do not contain genes that are essential for life, but they may contain genes that encode proteins that help them survive and propagate. Resistance factors = proteins that protect them against antibiotics.
