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A complete restriction digestion of a circular plasmid (5000bp) was carried out with HindIII, BamHI and EcoRIindividually. Restriction digestion yielded following fragments.
Plasmid + HindIII’→ 1200bp and3800bp
Plasmid + BamHI’→ 5000bp
Plasmid + EcoRI’→ 2500bp
The number of sites for EcoRI, BamHI-andHindIIIpresent on this plasmid are
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- EcoRI-2, BamHI-1, HindIII-2
- EcoRI-1, BamHI-1, HindIII-2
- EcoRI-3, BamHI-2, HindIII-1
- EcoRI-2, BamHI-2, HindIII-1
Correct Option: A
The given plasmid sequence is 5000bp long. When it is digested with Hind III, it produces 2 fragments of 1200bp and 3800bp. This means that Hind III cuts the plasmid in two different sites. So Hind III has 2 sites in plasmid. When digested with Bam HI, it produces one fragment of 5000bp. This means Bam HI has only 1 recognition site on the plasmid sequence. Eco RI cuts the fragment in two equal halves of 2500bp each. Hence Eco RI also has 2 sites of recognition on the plasmid.
