Explanation: When controlled by a strong promoter, reporter genes are often used as markers to confirm stable or transient transformation.

Explanation: The first reporter gene to be used in animal cells, derived from E.coli transposons Tn9; it has also been used to a certain extent in plants.

Explanation: CAT gene encodes the enzyme chloramphenicol acetyltransferase, which confers resistance to antibiotic chloramphenicol.

Explanation: Transient transformation can be achieved using replicon vectors that contain origins of replication derived from certain viruses of the polyomavirus family such as SV40.

Explanation: These viruses cause lytic infections, during the infection cycle viral gene products accumulate at high levels. Hence this strategy is used to produce recombinant proteins.

Explanation: SV40 was the first animal virus to be characterized in detail at the molecular level and for this reason, it was also the first to be developed as a vector.

Explanation: Simian Virus 40 (SV40) has a small icosahedral capsid and a circular double-stranded DNA genome of approximately 5 kb. It contains the early genes and the late genes.

Explanation: Transcription in SV40 is controlled by a complex regulatory element located between the early and late regions, and this includes early and late promoters, an enhancer and the origin of replication.

Explanation: During the first stage of SV40 infection cycle, the early transcript produces two proteins, known as large T and small t tumor antigens.

Explanation: The function of T-antigen is particularly important as this protein binds to the viral origin of replication and is absolutely required for genome replication.

Explanation: The T-antigen also acts as an oncoprotein, working with the host cell’s cycle machinery and causing uncontrolled cell proliferation.

Explanation: Human BK virus causes latent infections in which the viral genome is maintained as a low to moderate copy-number replicon that does not interfere with host cell growth.

Explanation: Epstein-Barr virus causes latent infections in which the viral genome is maintained as a low to moderate copy-number replicon that does not interfere with host cell growth.

Explanation: Polyadenylation signals are terminators required in eukaryotic genes to generate a defined 3’ end to the mRNA.

Explanation: Poly-adenyl sites from the Simian 40 Virus early transcription unit or mouse beta-globin gene are often incorporated into mammalian expression vectors.