Genome- data sets describing the complete dna sequence. Shotgun sequencing- breaking large genomes into tens of thousands of relatively tiny pieces: using restriction endonucleases to cut a genome into pieces about 160 kilobases. Fragments generated by different restriction endonucleases will overlap. insert fragments into a circular dna molecules (bac) bacterial artificial chromosome. Grow in e. coli cells to obtain large numbers of each fragment. Genome is broken down into two manageable levels: 1-kb segments in plasmids: overlaps occur because different restriction endonucleases were used to fragment the 160-kb segments, arrange each 160-kb segment in its correct position along the chromosome, based on regions over overlap. Lateral gene transfer- transfer of dna between two different species, especially distantly related species. Commonly occurs among bacteria and archaea via plasmid exchange; also can occur in eukaryotes via viruses and some other mechanisms. Plasmids become integrated into the main chromosome. Bacteria and archaea take up raw pieces of dna from the environment.