Abstract: A polynucleotide marker reagent is described for use in DNA and RNA size determination.

Abstract: A gel displacement comb and method for using the same to form multiple sample-wells on a gel within a horizontal electrophoresis device are disclosed. The comb comprises a base and a plurality of regularly spaced teeth projecting linearly from the base, the teeth being essentially of trapezoidal shape, separated by triangular spaces having a pointed apex such that the height H of the triangular space and the width B of the base of the triangle space satisfy the following equations:H=T-D, B<1/2Hwherein T represents the thickness of the gel and D represents a predetermined distance between the bottom of the gel and the end of the teeth when the comb is inserted in the electrophoresis device.