1 You have two preparations of the same plasmid one of which

1. You have two preparations of the same plasmid, one of which runs much faster in a gel than the other. If the plasmids have exactly the same number of base pairs, why do you think they run at such different mobilities?

2.What is the difference between a commercial vector and a natural plasmid?What is the difference between a commercial vector and a natural plasmid?

Solution

Please find the answers below:

Part 1: The size and orientation of a plasmid determine the way it runs on an agarose gel. For two plasmids of same molecular weight, one with supercoiled structure will run faster than one with linear or relaxed plasmid. This is because in a plasmid with supercoiled structure, the compactness is very high which promotes easy migration of whole plasmid across the gel. On the contrary, a linear or relaxed plasmid has moderate to low running speed on agarose gel because it takes longer time to traverse through the pores of the agarose gel.

According to the information in the question, two plasmids of same size are made to run on the gel out of which one runs slower. It can be deciphered from the above given information that though the size and number of base pairs of the slow running plasmid is same as that of the fast running plasmid, its conformational structure might be linear or relaxed superhelix which makes it run slower on the gel.

Part 2: Technically, plasmids can be differentiated into two types as described below:

1. Natural plamid: These are naturally occuring plamids which confer some specific biological functions to prkaryotic cells by natural transfer of plasmid from one microbe to another. The specific biological features can be antibiotic resistance, sex determination, mutation, toxicity resistance, recombination etc.

2. Artificial plasmid: In order to exploit the natural features of a plasmid via their ability to transform a microbe by physical transfer of a plasmid from one microbe to another, researchers have modified some plamids by recombinant DNA technology by insertion/deletion events leading to generation of a plasmid of required features. These artificial plasmids are routinely used for genetic engineering purpose such as expression of a target gene for protein expression, metabolite production, hormone synthesis etc.

The differences between a commercial vector and a natural plasmid can be found as below:

1. Commercial vector: A commercial vector is an artifically designed circular DNA structure which has small size, specific insertion sequences, restriction enzyme digestion/insertion sites, sites for origin of replication, site for insertion of selectable markers along with sites of insertion for gene of interest. These vectors are specifically designed for transfer of very small to very large genes of interest across a variety of organisms for research and analysis purpose.

2. A natural plasmid: A natural plasmid is a biologically naturally occuring double stranded circula DNA which imparts some specific properties to a microbe such as determination of sex, recombination frequency, antibiotic resistance, toxicity etc. These plamsids represent the basic features of genetic recombination in small microbes which normally do not undergo sexual reproduction. They also help in transport of genes across the microbial population and help generate biological variation and evolution.