question archive Harry purifies his plasmid and then sends a small amount of it to be sequenced
Harry purifies his plasmid and then sends a small amount of it to be sequenced
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Harry purifies his plasmid and then sends a small amount of it to be sequenced. The results from the sequencing show that he has correctly inserted the youngase DNA sequence into the plasmid. He then transforms bacteria with the plasmid, but transformation usually only occurs in a few cells. Harry knows he has to check for bacteria cells that have taken up the new plasmid. On able to do it, he takes a small amount of the bacteria and spreads them evenly on a Petri dish so that each individual cell is by itself and has room to divide, producing genetically identical cells. After a day at 37°C, each cell will have divided enough that a colony of cloned cells will be big enough to be seen with the naked eye on the Petri dish. Wild type bacterial colonies are white circles about the size of a pin head.
i. If Harry was successful at getting some of the bacteria to express the youngase gene, how would you expect the transformed bacteria colony to look? Explain your reasoning. (Add citations)
NOTE: "youngase" is a a fake name the professor used, FYI. She is using Harry Potter on all her questions and she made up that name.
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In this case blue white screening was performed to screen the wild type and transformed cells. The wild cells are devoid of the plasmid. So there is no question of having the β-galactosidase gene.
The colonies which contain the plasmid will have the functioning β-galactosidase gene and will be turned blue, due to the β-galactosidase activity. The presence of an active β-galactosidase is detected by means of X-gal (colourless analog of lactose) which will be cleaved by β-galactosidase enzyme to produce 5-bromo-4-chloro-indoxyl, that spontaneously dimerizes along with oxidizes to generate a bright blue insoluble pigment (5,5'-dibromo-4,4'-dichloro-indigo). [Note: The youngase DNA sequence is inserted into the plasmid in a region outside Lac Z(β-galactosidase producing gene)]
