Radiobutton HELP!!

[Rbtns]

Hi, I'm trying to use Radiobuttons with Tkinter. I've used them before,
but never two lists of them at one time.  The problem I am having is
that everytime I make a selection in one radiobutton list, the program
automatically makes that same selection for the other list. I have
included sample code to illustrate:

from Tkinter import *

root = Tk()
root.title('Radio Button Test')

sel1 = -1
sel2 = -1

menubar = Menu(root)
sel1menu = Menu(menubar, tearoff=0)
sel2menu = Menu(menubar, tearoff=0)

for a in range(3):

sel1menu.add_radiobutton(label='Select'+str(a),variable=sel1,value=a)
for a in range(5):

sel2menu.add_radiobutton(label='Select'+str(a),variable=sel2,value=a)

menubar.add_cascade(label='Select1',menu=sel1menu)
menubar.add_cascade(label='Select2',menu=sel2menu)

root.config(menu=menubar)

root.mainloop()

If anyone knows how to do this, please don't hesistate to respond. Thank
you very much.