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Induction of beta-galactosidase

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Induction of �-galactosidase Hypothesis and aims By carrying out this experiment I plan to show that in the absence of lactose, the enzyme �-galactosidase will not be made and the mixture I use to test for this will be colourless. The main aim of the experiment is to demonstrate practically the switching on of a gene. Method To test this hypothesis I will use the bacterium E.Coli which produces the enzyme �-galactosidase when lactose is present. I will go into the details of how and why later. This is the apparatus, equipment and method I will use. A tick indicates that the named substance will be put into the test tube in question. Test tube 1cm3 E. Coli without lactose 1cm3 E. Coli with lactose 1cm3 Distilled water 1cm3 �-galacto- sidase 1cm3 ONPG 5 drops Methyl- benzene 5cm3 Sodium Phosphate Colour at start Colour at end 1 ? ? ? ? Colourless 2 ? ? ? ? Colourless 3 ? ? ? ? Colourless 4 ? ? ? ? Yellow The lac operon is the classic example of gene regulation, in which the production of �-galactosidase (lactase) ...read more.


coli and it is not cleared up. It could (due to its colourless appearance) look like water. Someone else may then clear it up themselves and not wash their hands thoroughly afterwards or not use disinfectant to completely get rid of the bacteria. This could lead to the E. coli being digested which may lead to serious bacterial illness. * After doing the experiment, hands should be washed thoroughly with soap. The detergents in soap help to break open the walls of the bacteria, in essence, killing them and therefore putting a stop to any risk they may cause the person. The techniques used throughout the practical work should avoid contamination of the experiment by microorganisms or spores from any other sources, and protect the person carrying out the experiment and others from being contaminated. The correct methods for handling microorganisms are called aseptic techniques and the one employed for this experiment is listed below. Bottle necks When using any glass bottle or test tube, the neck should be flamed when opening or closing. To do this: 1. Loosen the top - i.e. the lid, cap or cotton wool plug. ...read more.


Test Tube 4 - �-galactosidase enzyme - this second control will be yellow from the beginning as �-galaactosidase is already present and therefore this will prompt the change of ONPG to ONP and G, creating the yellow colour. This control is the known positive result and will be used as a comparison to see if we have a positive result in test tubes 1 or 2. One limitation with this experiment is that it takes quite a long time to set it up. This meant that there was not time to do repeats of the experient, seriously decreasing its acceptability and validity. However, everyone in our class did the experiment at the same time and used the same method so I will use their results as my 'repeats.' If I'd have had time I wouldhave done the repeats myself to avoid any differences that might occur in procedure due to variety between the people carrying out the experiment. However, this was not practical. Therefore, other people's results will suffice for my needs in cross-checking the conclusions I reach. The apparatus was generally suitable. There was nothing to do with apparatus and equipment at this stage that created a lot of error or that should be changed to get a better set of results. ...read more.

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