Northern blot band size calculation - (May/21/2007 )
Hello all,
This is my first post here. How exciting to be able to discuss lab issues with all of you!!!
I would like to know if anyone could give me an insight to how to determine the size of an unknown band on a northern blot gel. I just developed my film. I know the size of the 28S and 18S bands (4718 [2.0cm] and 1874bp [2.9cm], respectively). A lab member told me that the calculation is based on proportions. Do anybody know how do I calculate the size of my unknown band (3.9cm)?
Thank you so much!!! 
-peabiria-
QUOTE (peabiria @ May 21 2007, 11:22 AM)
Hello all,
This is my first post here. How exciting to be able to discuss lab issues with all of you!!!
I would like to know if anyone could give me an insight to how to determine the size of an unknown band on a northern blot gel. I just developed my film. I know the size of the 28S and 18S bands (4718 [2.0cm] and 1874bp [2.9cm], respectively). A lab member told me that the calculation is based on proportions. Do anybody know how do I calculate the size of my unknown band (3.9cm)?
Thank you so much!!!
This is my first post here. How exciting to be able to discuss lab issues with all of you!!!
I would like to know if anyone could give me an insight to how to determine the size of an unknown band on a northern blot gel. I just developed my film. I know the size of the 28S and 18S bands (4718 [2.0cm] and 1874bp [2.9cm], respectively). A lab member told me that the calculation is based on proportions. Do anybody know how do I calculate the size of my unknown band (3.9cm)?
Thank you so much!!!
One method is to imagine a graph with distance migrated on the x-axis and size on the y-axis. With your 28S and 18S bands you can plot two points on the graph and deduce the equation of the line between them (y=mx+ b ). Plug the distance traveled from your band of interest into this equation and solve for y to get its size.
I'm sure there's a more elegant way of doing it, but this works for me.
-Cassio-