difference in band sizes ! - why ??? (May/19/2011 )

Dear All,

am having weired PCR results, and would really appreciate it if anyone can help.

kindly, see the attached gel picture.

the samples:
1- NTC.
2- +ve control.
3-11 different tissue extracts tested for the presence of a virus.

the expected band size is 338bp, which is the observed in the positive control.
while all the other tissue samples showed this < 300 bp band ...

why ? if am to think that there is s.th wrong with the run,
i wouldn't have the right band size for the positive control, right ??
and these tissue samples are different i.e some : ovary others: trachea ...
so why to see the same size in all of them regardless of the type ??

today too it happened with another PCR run;
to have the right band size with the positive control while having another band size in all the tissue type samples.

thanks for the time spent reading my post.

grateful.

What is your positive control? A tissue isolate, purified virus or what? What part of viral genome do you use for PCR?

Trof on Fri May 20 07:22:24 2011 said:

thanks Trof for ur passing

my positive control, is : allantoic fluid + virus.

my samples are tissues : as trachea, ovary, kidney ...

detecting nucleocapsid gene in infectious bronchitis virus.
But in yesterday's run i got the same results detecting Spike gene.

-nightingale-