PROBLEM WITH SOUTHERN BLOT

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Saint
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PROBLEM WITH SOUTHERN BLOT

Hi guys!Well, I have a problem with a new thecnique for me, I'll describe you my protocol before my doubt. First , I extract RNA from brain slices, there's no problem with that, 260/280 ratio is good, about 1.96, and its integrity in agarose gels looks like fine  . Then, I proceed to cDNA synthesis with Superscript III kit, having two negative controls: one contains RNA, oligo DT, dNTPs, water (Mix 1) as well as 10 XRT buffer, 25 mM MgCl2, DTT, RNAase out (Mix 2) but not the enzime (Superscript III) and the other one consists in a tube containing Mix 1 and Mix 2, including enzime but without RNA. After DNA synthesis, I perfom a PCR assay for GAPDH to verify a correct cDNA amplification and finally I run an agarose gel and the results are as follow: I can identify bands corresponding to GAPDH in the lane of my sample, but in negative control lane,where I did not put enzime (Superscript III) there is a band and I can´t explain this, because if there's no enzime, how can it show a band? Someone can help me with that?all suggestions to resolve my trouble are welcome.Thanks for advantage.