Q) Explain why plasmids are useful as cloning vectors
Main points | |
Key idea: | What are plasmids |
· Small extra-chromosomal circular DNA mol (originates fr bacteria) · Properties to role: with known restriction maps + DNA sequences to facilitate insertion of a gene/DNA of interest to form a recombinant vector | |
Key idea: | Property (1) Multiple cloning site (MCS) |
· Most plasmid - modified to contain a MCS · MCS - comprises of several unique restriction enz recognition sites, facilitates insertion of gene seq into vector (without fragmenting vector) | |
Key idea: | Property (2) Origin of replication (Ori) |
· Ori allows vector to replicate independently fr host chrom · Result: gene seq replicated tog - more copies of gene formed | |
Key idea: | Property (3) Selection markers |
· Role : confer well-defined phenotype on host organism, for easy identification of host cells containing gene or recombinant vector · Example 1 : antibiotic resistance genes (e.g. ampicillin resistance gene and tetracycline resistance gene) · Example 2 : Lac Z gene | |
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Isolation of correct transformed colonies often requires more than 1 selection marker (refer to production of insulin essay) (v) Some of my abbreviations are meant for revision purpose and may not be acceptable for exams | |
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