1. Identify the band on the gel that corresponds to β-galactosidase. To do this, remember two things: 1) the predicted molecular weight (MW) of the β-gal monomer is 116 kDa; and 2) β-gal should be increasing in abundance (thicker, darker band on the gel) over the period of IPTG induction. You will likely be able to identify the β-gal band in more than one lane of the gel, but you will just need to measure the migration distance using the lane in which the band is most obvious. Since the band will be thick, measure the distance from the bottom of the well to the middle of the β-gal band. You will use this measurement to calculate the MW of β-gal based on the graph of the migration distances of the MW ladder bands that you will generate in part IB. 2 . The rate of migration of a protein through an SDS-PAGE gel is related to its molecular weight through an inverse logarithmic relationship: that is, if you plot the log10 of the MW of each standard on the y-axis against its migration distance on the x-axis, you should obtain a line with a negative slope. If you obtain the equation of the line through linear regression, you can then use that equation to solve for the log10(MW) of any band on the same gel by plugging in its measured migration distance for “x;” lastly, you can take the antilog of the answer to obtain an estimate of that protein’s molecular weight. The instructions below describe how to do this in Microsoft Excel. You should submit your Excel spreadsheet as an attachment on Blackboard along with your answers to the discussion questions in Part II below; be sure also to show your work for the MW calculation, either in your document with your discussion question answers or using the formula feature on your Excel spreadsheet.