Final answer:
Molecular weight is estimated on a gel electrophoresis diagram by comparing the distance that sample bands have traveled to the known distances of standard marker bands. For DNA, travel distances are plotted against the log of the sizes in kilobases (kb), creating a standard curve from which DNA sizes can be interpolated. The separation is influenced by factors like the gel's pore size and the molecule's shape and charge.
Step-by-step explanation:
Molecular weight can be estimated by reading a gel electrophoresis diagram by comparing the sample bands to a molecular weight standard that includes fragments of known size. When DNA is run through a gel, shorter molecules travel further than longer ones due to reduced friction.
To estimate the size of DNA fragments, one can measure the distance each band has traveled from the well and compare it to the distances traveled by the molecular weight standard's bands.
Notably, when constructing a plot of log(kb) versus distance traveled using a DNA ladder, the linear relationship allows for the determination of the unknown DNA fragment sizes in the sample lanes.
Agarose gel electrophoresis is commonly used for DNA separation, while polyacrylamide gel electrophoresis is preferred for protein separation. Factors like the pore size of the gel, which can be controlled by the ratio of acrylamide to bis-acrylamide, significantly contribute to the separation process.
For proteins, two-dimensional gel electrophoresis employing Isoelectric Focusing (IEF) followed by Polyacrylamide Gel Electrophoresis (PAGE) can resolve complex mixtures, where proteins are separated based on isoelectric point and molecular weight.