Explanation: The replicase protein produces a negative-sense complementary strand, which in turn acts as a template for the production of full-length daughter genomes.

Explanation: The negative strand contains an internal promoter which allows the synthesis of a subgenomic positive sense RNA containing the capsid polyprotein gene.

Explanation: Replication-competent vectors have been constructed in which an additional subgenomic promoter is placed either upstream or downstream of the capsid polyprotein gene.

Explanation: If foreign DNA is introduced downstream of the subgenomic promoter, the replicase protein produces two distinct RNAs, one corresponding to the transgene.

Explanation: Insertion vectors tend to be unstable and have been largely superseded by replacement vectors in which the capsid polyprotein is replaced by a transgene.

Explanation: The first 120 b of Sindbis and SFV structural polyprotein genes includes a strong enhancer of protein synthesis which increases the yield of recombinant protein.

Explanation: In many vectors, the enhancer region is included so that the foreign gene is expressed as an N-terminal fusion protein.

Explanation: A versatile Sindbis replicon vector, pSinRep5 vector is a plasmid containing bacterial backbone elements along with several other genes.

Explanation: There is an SP6 promoter upstream of the replicase genes and the expression cassette for generating full length in vitro transcripts.

Explanation: There is a second set of restriction sites downstream from the polylinker, allowing the vector to be linearized prior to in vitro transcription.

Explanation: The entire alphavirus genome can be placed under the control of standard eukaryotic vector SV40 and cells can then be transfected with DNA.

Explanation: Transduction is a more suitable delivery procedure for gene therapy applications, using alphaviral vectors along with defective helper virus.

Explanation: Vaccinia virus is closely related to variola virus, the agent responsible for smallpox. Worldwide vaccination of this virus led to the elimination of smallpox.

Explanation: Unusually for a DNA virus, the poxviruses replicate in the cytoplasm rather than the nucleus. The virus packages and encodes its DNA all by itself.

Explanation: The poxviruses have a complex structure and a large double-stranded linear DNA genome. The virus packages and encodes its DNA all by itself.