Could be that your gel is too dense for your sample, or that the sample size is too large for the agarose concentration used. does this happen for the ladder as well, or is it sample only? if sample is too big for the gel, it will stay in the pocket, thereby illumination the pocket.

Hello Shivangi ..

There could be many reasons. Some of which are given below.

1) The DNA may not have been extracted properly or the gel preparation may be poor. The comb may not have been placed correctly or the gel must have been disturbed during the removal of the comb. Because of these reasons, the DNA is unable to come out from the well.

The wells may have been broken during sample loading or the air bubbles may have been formed during gel casting. These air bubbles inside the wells could hinder DNA from migrating towards the positive pole.

2) Re-using the gel may limit the migration of DNA.

3) The concentration of DNA may be very high in the well.

4) The DNA may be highly contaminated with proteins.

Best.

A picture would help to clarify. Keep in mind that other non-DNA substances can light up in UV.

Another thing that may be happening is simple reflection of light in the gel (not a real band, just an image artifact)

What does your DNA ladder look like? If the ladder looks as expected, then you can rule out things like not turning on the electric current.

And a picture would really help!

I have attached the gel picture here.

Well, your DNA ladder looks great. To me, the bands up by the well look like gDNA. There are other molecules that will light up in a gel and show up (secondary metabolites etc.)

What size is the band you are hoping to see?

If your bands are faint it can help to remove the gel from the running tray as those do absorb some of the UV light.

I am isolating a 9600bp DNA

ok, that's a nice reasonable size. Is it plasmid, PCR product?

It would help to know the sizes of the ladder bands here too.