The vector, pCMV6-XL4, can express cloned genes from the CMV promoter (shown as pCMV in the map). The plasmid size is 4.7 kb with the multiple cloning site as shown above. Downstream of the cloning site is the hGH poly A (human growth hormone poly A) site. The F1 origin is the filamentous phage origin of replication which allows for recovery of single-stranded plasmid when E. coli are co-infected with helper phage. The ColE1 origin is the origin of replication which is used in the absence of helper phage. The SV40 Ori is the origin of replication used in tissue culture cells. The T7 and M13 promoters are useful for generating sense and antisense transcripts using in vitro transcription. They can also be used as primer annealing sites for sequencing cDNA clones.