dna bands are not developed.

And?
What is your question?
what is the connection to apoptosis?

if you are talking about the DNA fragmentation assay, you can check out these protocols and compare to your protocol.

Did you put Ethidium Brimode in your gel and/or running buffer, or did you post-stain the gel?

Did you wash the gel in running buffer without EtBr after you stained it? You might have over destained it?

Are you sure you did not slip up and make the gel with water and not TAE? Believe me it does happen by accident from time to time!

Did you run the gel too far/long and run all the band off the gel?

load another gel with EtBr in the gel and the running buffer. Then check it after 10 mins to make sure your DNA has eneterd the gel. then keep running it.

when did you add ethidium bromide? before or after running the gel?

aagaman said:

dna bands are not developed.

For proper trouble shooting refer 'Molecular cloning' by Sambrook.
You might solve your problem without anyone's help in simple expt's like this .....:)