1. Biology of genetic engineering Host cell types. Host cell types 1. Prokaryotic hosts; such as E. coli 2. Eukaryotic hosts; range from microbes, such as yeast and algae, to cells from us. Vectors (plasmids, phages).

2. Plasmids Circular DNA molecules. Relatively small. Mostly extra-chromosomal. Found naturally, in bacteria and some yeasts and modified for genetic engineering. Plasmids can be classified 1. Conjugative plasmids; mediate their own transfer between bacteria. 2. Non-conjugative plasmids; not self- transmissible.

3. Plasmids Plasmids can be further classified based on their copy number into: 1. Low copy number plasmids; replicate closely tied to the host cell DNA replication. 2. High copy number plasmids; replicate independent from host cell DNA replication. Example plasmid pBR322pBR322