BIOL 1010 Lecture Notes - Virus, Hfr Cell, Plasmid
Document Summary
The major component of the bacterial genome is one double-stranded, circular dna molecule. E. coli genome consists of 4. 6 million nt pairs, representing 4300 genes (size of genome is 100:1 vs. virus 1:1000) Densely packed, it forms the region called nucleoid. Bacterial cells divide by fission (20 min per division in optimal condition) proceeded by replication of the chromosome. Fission is asexual process-most of the bacteria in a colony are genetically identical to the parent cell. Spontaneous mutation rate of 10-7 per cell division result in 2000 e. coli mutants in a human colon where 2x1010 cells are produced per day. Thus new mutations, although rare, can have a significant impact on genetic diversity when reproductive rates are very high. The prokaryotic chromosome is a single dna molecule that first replicates, then attaches each copy to a different part of the cell membrane. When the cell beings to pull apart, the replicate and original chromosomes are separated.