Following figure shows one of the artificial plasmids constucted to act as a vector.
(i) With reference to above figure explain the importance of the plasmid having a single target site for a particular restriction enzyme, such as Bam HI.
(ii) The genes for ampicillin resistance and tetracycline resistance on the plasmid allow .the genetic engineer to distinguish between bacteria that have taken up different circuits of DNA.
Complete the table to show whether bacteria which have taken up each of the different circuit of DNA are resistant to ampicillin, to tetracycline or to both. Show presence of resistance with a tick (right) and absence of resistance with a cross (wrong).
(iii) (a) Explain why genes for antibiotic resistance are now rarely used as markers in gene technology.
(b) Describe the use of one alternative marker gene that can be used instead of antibiotic resistance gene.
(i) Single target site is present for a particular restriction enzyme. If more than one site is present, then more cuts would fragment the plasmid.
(iii) (a) Now a days antibiotic resistance genes as markers are not used as they create more risk of plasmids to be taken up by other bacteria and passing on resistant gene to other bacteria.
It may spread the antibiotic resistance in many bacteria.
(b) Reporter genes are used now a days instead of antibiotic resistance genes. These genes have an ability to produce colour in the presence of chromogenic substrate.